Artificially structured unit cells providing localized b1 magnetic fields for mri and nmr devices

ABSTRACT

Described embodiments include a system, apparatus, and method. An apparatus includes an array of at least two groups of at least two artificially structured electromagnetic unit cells. Each group of the at least two groups configured to be respectively linearly arranged with respect to the z-axis of the bore of MRI or NMR device. Each group of the at least two groups of artificially structured electromagnetic unit cells configured to transform an incident pulse of radiofrequency electromagnetic waves into a pulse of radiofrequency magnetic field B 1  orientated transverse to a segment of the z-axis and spatially proximate to the group. The apparatus includes a radiofrequency electromagnetic wave conducting structure configured to selectably distribute a received pulse of radiofrequency electromagnetic waves to a group of the at least two groups.

If an Application Data Sheet (ADS) has been filed on the filing date ofthis application, it is incorporated by reference herein. Anyapplications claimed on the ADS for priority under 35 U.S.C. §§119, 120,121, or 365(c), and any and all parent, grandparent, great-grandparent,etc. applications of such applications, are also incorporated byreference, including any priority claims made in those applications andany material incorporated by reference, to the extent such subjectmatter is not inconsistent herewith.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the earliest availableeffective filing date(s) from the following listed application(s) (the“Priority Applications”), if any, listed below (e.g., claims earliestavailable priority dates for other than provisional patent applicationsor claims benefits under 35 USC §119(e) for provisional patentapplications, for any and all parent, grandparent, great-grandparent,etc. applications of the Priority Application(s)).

PRIORITY APPLICATIONS

None.

If the listings of applications provided above are inconsistent with thelistings provided via an ADS, it is the intent of the Applicant to claimpriority to each application that appears in the DomesticBenefit/National Stage Information section of the ADS and to eachapplication that appears in the Priority Applications section of thisapplication.

All subject matter of the Priority Applications and of any and allapplications related to the Priority Applications by priority claims(directly or indirectly), including any priority claims made and subjectmatter incorporated by reference therein as of the filing date of theinstant application, is incorporated herein by reference to the extentsuch subject matter is not inconsistent herewith.

SUMMARY

For example, and without limitation, an embodiment of the subject matterdescribed herein includes an apparatus. The apparatus includes an arrayof at least two groups of at least two artificially structuredelectromagnetic unit cells. Each group of the at least two groups isconfigured to be arranged in a respective plane perpendicular to thez-axis of the bore of a magnetic resonant imaging or a nuclear magneticresonant device. Each group of the at least two groups of artificiallystructured electromagnetic unit cells configured to transform anincident pulse of radiofrequency electromagnetic waves into a pulse ofradiofrequency magnetic field B₁ orientated transverse to a segment ofthe z-axis and spatially proximate to the group. The apparatus includesa radiofrequency electromagnetic wave conducting structure configured toselectively distribute a received pulse of radiofrequencyelectromagnetic waves to a group of the at least two groups.

In an embodiment, the at least two artificially structuredelectromagnetic unit cells of each group of at least two artificiallystructured electromagnetic unit cells include at least two assemblagesof artificially structured electromagnetic unit cells. Each assemblageof the at least two assemblages of artificially structuredelectromagnetic unit cells including (i) a first artificially structuredelectromagnetic unit cell configured to transform an incident pulse ofradiofrequency electromagnetic waves into a pulse of the radiofrequencymagnetic field B₁ and (ii) a second artificially structuredelectromagnetic unit cell configured to transform the incident pulse ofradiofrequency electromagnetic waves into an electric field Ecounteracting a non-vanishing electric field generated by the firstartificially structured electromagnetic unit cell.

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a method. The method includes receiving apulse of radiofrequency electromagnetic waves from a radiofrequencysignal generator or signal synthesizer component of a magnetic resonantimaging or a nuclear magnetic resonant device. The method includesdistributing the received pulse of radiofrequency electromagnetic wavesas an incident pulse of radiofrequency electromagnetic waves to aselected group of an array of at least two groups of at least twoartificially structured electromagnetic unit cells. The method includestransforming, using the at least two artificially structuredelectromagnetic unit cells of the selected group, the incident pulse ofradiofrequency electromagnetic waves into a localized pulse of aradiofrequency magnetic field B₁ orientated transverse to the z-axis ofa bore of the magnetic resonant imaging or the nuclear magnetic resonantdevice. The localized pulse of the radiofrequency magnetic field B₁having a magnetic field intensity sufficient to excite a detectablemagnetic resonance in magnetically active nuclei located within at leasta portion of the transverse segment of an examination region locatedwithin the bore.

In an embodiment, the method includes selecting the group of at leasttwo groups of at least two artificially structured electromagnetic unitcells in response to data indicative of a location along the z-axis of atransverse slice selected for examination.

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a system. The system includes an array of atleast two groups of at least two artificially structured electromagneticunit cells. Each group of the at least two groups configured to berespectively linearly arranged with respect to the z-axis of the bore ofa magnetic resonant imaging or a nuclear magnetic resonant device. Eachgroup of the at least two artificially structured electromagnetic unitcells respectively configured to transform incident pulses ofradiofrequency electromagnetic waves into pulses of radiofrequencymagnetic field B₁ orientated transverse to a segment of the z-axis andspatially proximate to the group. The system includes a radiofrequencyelectromagnetic wave conducting structure configured to distribute thepulses of radiofrequency electromagnetic waves as the incident pulses ofthe radiofrequency electromagnetic waves to a selectable group of the atleast two groups in response to a B₁ localization control signal. Thesystem includes a control circuit configured to generate the B₁localization control signal defining a respective power distribution andphase delays (including zero and non-zero phase delays) of a particularincident pulse of radiofrequency electromagnetic waves to each group ofthe at least two groups. The respective power distribution collectivelydefining a particular pulse of radiofrequency magnetic field B₁localized to a selected arbitrary examination segment transverse to thez-axis and within an examination region of the bore. The localizedmagnetic field B₁ having an intensity sufficient to excite a detectablemagnetic resonance in magnetically active nuclei located within theselected arbitrary examination segment.

In an embodiment, the system includes a receiver configured to receivedata indicative of a location along the z-axis of the transverse sliceselected for examination. In an embodiment, the system includes a unitcell controller configured to electronically control the at least twoelectronically controllable, artificially structured electromagneticunit cells of each group of the at least two groups in response to thegradient component of the control signal.

For example, and without limitation, an embodiment of the subject matterdescribed herein includes a method. The method includes receiving apulse of radiofrequency electromagnetic waves from a radiofrequencysignal generator or signal synthesizer component of a magnetic resonantimaging or a nuclear magnetic resonant device. The method includesgenerating a B₁ localization control signal defining a respective powerdistribution of the pulse of radiofrequency electromagnetic waves toeach group of the at least two groups of at least two artificiallystructured electromagnetic unit cells. Each group of the at least twogroups is configured to be sequentially positioned in a respective planetransverse to the z-axis of the bore of the magnetic resonant imaging orthe nuclear magnetic resonant device. The respective power distributioncollectively defining a pulse of radiofrequency magnetic field B₁localized to a selected arbitrary examination segment transverse to thez-axis and within an examination region of the bore. The method includesdistributing the received pulse of radiofrequency electromagnetic wavesas an incident pulse of radiofrequency electromagnetic waves to a groupof the at least two groups in accord with the B₁ localization controlsignal. The method includes transforming, using the at least twoartificially structured electromagnetic unit cells of the group, theincident pulse of radiofrequency electromagnetic waves into a localizedpulse of a radiofrequency magnetic field B₁ orientated transverse to theselected arbitrary examination segment and having an intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within the selected arbitrary examination segment.

In an embodiment, the method includes selecting the arbitraryexamination segment responsive to data indicative of a location of aslice along the z-axis a orientated transverse selected for examination.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the drawings and the followingdetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an environment 200 that includes an example magneticresonant imaging or a nuclear magnetic resonant device 300, includingsome of its systems;

FIG. 2 illustrates an example of the magnetic resonant imaging ornuclear magnetic resonant device 300 that includes an apparatus 310;

FIG. 2A illustrates an example of a cross-sectional view of the magneticresonant imaging or a nuclear magnetic resonant device 300.

FIG. 2B illustrates an example of a view through the bore 316 of themagnetic resonant imaging or a nuclear magnetic resonant device 300.

FIG. 3 illustrates alternative embodiments of artificially structuredelectromagnetic unit cells 322;

FIG. 3A illustrates a unit cell 322A with concentric split ringsinsertion 324A.

FIG. 3B illustrates a unit cell 322B with a split ring insertion 324Bhaving shoulders at the split.

FIG. 3C illustrates a unit cell 322C with concentric box split rings324C insertion.

FIG. 3D illustrates a unit cell 322D with a conical helix insertion324D.

FIG. 3E illustrates a unit cell 322E with an interleaved “L” ringsinsertion 324E.

FIG. 3F illustrates a unit cell 322F with an “I” inclusion 324F withbroad shoulders.

FIG. 3G illustrates a unit cell 322G with an opposing box split ringsinsertion 324G.

FIG. 4 illustrates an example operational flow 400;

FIG. 5 illustrates an example apparatus 500;

FIG. 6 illustrates an example apparatus 605 configured to generate aradiofrequency magnetic field B₁ in a magnetic resonant imaging or anuclear magnetic resonant device;

FIG. 7 illustrates an example operational flow;

FIG. 8 illustrates an example operational flow 800;

FIG. 9 illustrates a system 902 that includes an embodiment of anexample apparatus 905 configured to generate a radiofrequency magneticfield B₁;

FIG. 10 illustrates an example operational flow 1000;

FIG. 11 illustrates an example apparatus 1100;

FIG. 12 illustrates an example apparatus 1205;

FIG. 13 illustrates an example operational flow 1300;

FIG. 14 illustrates an example operational flow 1400; and

FIG. 15 illustrates an example operational flow 1500.

DETAILED DESCRIPTION

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/257,175, entitled SUB-NYQUISTHOLOGRAPHIC APERTURE ANTENNA CONFIGURED TO DEFINE SELECTABLE, ARBITRARYCOMPLEX ELETROMAGNETIC FIELDS, naming Pai-Yen Chen et al. as inventors,filed on Apr. 21, 2014, is related to the present application. Thatapplication is incorporated by reference herein, including any subjectmatter included by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/257,187, entitled SUB-NYQUISTHOLOGRAPHIC APERTURE ANTENNA CONFIGURED TO DEFINE SELECTABLE, ARBITRARYCOMPLEX ELETROMAGNETIC FIELDS, naming Pai-Yen Chen et al. as inventors,filed on Apr. 21, 2014, is related to the present application. Thatapplication is incorporated by reference herein, including any subjectmatter included by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/257,386, entitled SYSTEM WIRELESSLYTRANSFERRING POWER TO A TARGET DEVICE OVER A TESTED TRANSMISSIONPATHWAY, naming Pai-Yen Chen et al. as inventors, filed on Apr. 21,2014, is related to the present application. That application isincorporated by reference herein, including any subject matter includedby reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/257,415, entitled SYSTEM WIRELESSLYTRANSFERRING POWER TO A TARGET DEVICE OVER A MODELED TRANSMISSIONPATHWAY WITHOUT EXCEEDING A RADIATION LIMIT FOR HUMAN BEINGS, namingPai-Yen Chen et al. as inventors, filed on Apr. 21, 2014, is related tothe present application. That application is incorporated by referenceherein, including any subject matter included by reference in thatapplication.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 12/286,740, entitled BEAM POWER FORLOCAL RECEIVERS, naming Roderick A. Hyde et al. as inventors, filed onSep. 30, 2008, is related to the present application. That applicationis incorporated by reference herein, including any subject matterincluded by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 12/286,737, entitled BEAM POWER WITHMULTIPOINT BROADCAST, naming Roderick A. Hyde et al. as inventors, filedon Sep. 30, 2008, is related to the present application. Thatapplication is incorporated by reference herein, including any subjectmatter included by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 12/286,755, entitled BEAM POWER WITHMULTIPOINT RECEPTION, naming Roderick A. Hyde et al. as inventors, filedon Sep. 30, 2008, is related to the present application. Thatapplication is incorporated by reference herein, including any subjectmatter included by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 12/286,741, entitled BEAM POWER WITHBEAM REDIRECTION, naming Roderick A. Hyde et al. as inventors, filed onSep. 30, 2008, is related to the present application. That applicationis incorporated by reference herein, including any subject matterincluded by reference in that application.

This application makes reference to technologies described more fully inU.S. Patent Application No. 61/455,171, entitled SURFACE SCATTERINGANTENNAS, naming Nathan Kundtz as inventor, filed Oct. 15, 2010, isrelated to the present application. That application is incorporated byreference herein, including any subject matter included by reference inthat application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 13/317,338, entitled SURFACE SCATTERINGANTENNAS, naming Adam Bily et al. as inventors, filed Oct. 14, 2011, isrelated to the present application. That application is incorporated byreference herein, including any subject matter included by reference inthat application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 13/838,934, entitled SURFACE SCATTERINGANTENNA IMPROVEMENTS, naming Adam Bily et al. as inventors, filed Mar.15, 2013, is related to the present application. That application isincorporated by reference herein, including any subject matter includedby reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/102,253, entitled SURFACE SCATTERINGREFLECTOR ANTENNA, naming Jeffrey A. Bowers et al. as inventors, filedDec. 10, 2013, is related to the present application. That applicationis incorporated by reference herein, including any subject matterincluded by reference in that application.

This application makes reference to technologies described more fully inU.S. patent application Ser. No. 14/226,213, entitled SURFACE SCATTERINGANTENNA ARRAY, naming Jesse R. Cheatham, III et al. as inventors, filedMar. 26, 2014, is related to the present application. That applicationis incorporated by reference herein, including any subject matterincluded by reference in that application.

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here.

FIG. 1 illustrates an environment 200 that includes an example magneticresonant imaging or a nuclear magnetic resonant device 300, includingsome of its systems. The magnetic resonant imaging or a nuclear magneticresonant device includes a permanent or superconducting magnetgenerating a z-axis magnetic field B₀. For example the permanent orsuperconducting magnet may generate a magnetic field B₀ of at least 0.5T. The magnetic resonant imaging or a nuclear magnetic resonant deviceincludes a gradient coil device creating a temporal linear gradient inthe magnetic field B₀ along the z-axis. In addition, the magneticresonant imaging or a nuclear magnetic resonant device includes a deviceor apparatus configured to generate a radiofrequency magnetic field B₁perpendicular to the z-axis.

FIG. 2A illustrates a cross-sectional view of magnetic resonant imagingor nuclear magnetic resonant device 300, and FIG. 2B illustrates a viewthrough a bore of the device (FIGS. 2A and 2B are collectively referredto herein as FIG. 2). FIG. 2 illustrates an example of the magneticresonant imaging or nuclear magnetic resonant device 300 that includesan apparatus 310. FIG. 2A is a cross-sectional view, and FIG. 2B is aview through the bore 316 of the magnetic resonant imaging or a nuclearmagnetic resonant device. The nuclear magnetic resonant device includesa permanent or superconducting magnet 312 and a gradient coil device314. The apparatus includes an array 320 of at least two artificiallystructured electromagnetic unit cells 322. Additional description of theunit cells in provided in conjunction with FIG. 3. The at least twoartificially structured electromagnetic unit cells are configured togenerate a pulse of radiofrequency magnetic field B₁ 328 orientatedtransverse to the quasistatic magnetic field B₀ parallel to the z-axis318 of the bore 316 of the magnetic resonant imaging or a nuclearmagnetic resonant device by transforming an incident pulse ofradiofrequency electromagnetic waves. The generated pulse havingmagnetic field intensity sufficient to excite a detectable magneticresonance in magnetically active nuclei located within at least aportion of an examination region located within the bore. The apparatusincludes a radiofrequency electromagnetic wave conducting structure 380configured to distribute a received pulse of radiofrequencyelectromagnetic waves as an incident pulse of radiofrequencyelectromagnetic waves to the at least two artificially structuredelectromagnetic unit cells. In an embodiment, the magnetic field B₀ iscreated by a primary magnet of the magnetic resonant imaging or thenuclear magnetic resonant device.

FIGS. 3A, 3B, 3C, 3D, 3E, 3F, and 3G illustrates alternative embodimentsof artificially structured electromagnetic unit cells 322 (FIGS. 3A, 3B,3C, 3D, 3E, 3F, and 3G are collectively referred to herein as FIG. 3).FIG. 3 illustrates alternative embodiments of artificially structuredelectromagnetic unit cells 322. In an embodiment, the artificiallystructured electromagnetic unit cells may include metamaterial unitcells. In an embodiment, the artificially structured electromagneticunit cells may include a metamaterial cellular architecture. In anembodiment, a metamaterial includes an artificially structured materialthat gains its properties from its structure rather than itscomposition. In an embodiment, a metamaterial includes a macroscopiccomposite of a periodic or non-periodic structure, whose function is dueto both its cellular architecture and chemical composition. Tie Jun Cuiet al. ed., Metamaterials: theory, design, and applications, 2 (Springer2010). In an embodiment, the artificially structured electromagneticunit cells have a cellular size less than the wavelength of aradiofrequency involved. In an embodiment, the unit cells arearbitrarily shaped unit cells. In an embodiment, the unit cells arestructured by artificial inclusions with a sub-wavelength size. In anembodiment, the array 320 of artificially structured unit cells respondsto electric and magnetic fields as a homogeneous structure or aneffective medium. In an embodiment, inclusions in a unit cell may bespecifically designed for dielectric permittivity, magneticpermeability, and index of refraction, and placed at a desired locationin the unit cell.

FIG. 3 illustrates example inclusions in unit cells. The unit cells maybe resonant or non-resonant. FIG. 3A illustrates a unit cell 322A withconcentric split rings insertion 324A. FIG. 3B illustrates a unit cell322B with a split ring insertion 324B having shoulders at the split.FIG. 3C illustrates a unit cell 322C with concentric box split rings324C insertion. FIG. 3D illustrates a unit cell 322D with a conicalhelix insertion 324D. FIG. 3E illustrates a unit cell 322E with aninterleaved “L” rings insertion 324E. FIG. 3F illustrates a unit cell322F with an “I” inclusion 324F with broad shoulders. FIG. 3Gillustrates a unit cell 322G with an opposing box split rings insertion324G. The selection of an inclusion for the unit cells 245 may be madeby those skilled in the art responsive to the particular designrequirements and materials available. Another example of inclusions inunit cells is the multi-turn rectangular planar spiral, or several suchspirals lying in different planes and connected by conducting vias. Whenmore than two such planar spirals are connected, they may be describedas “three-dimensional meander line”. The multi-turn rectangular spiralinclusions are described in more detail by Lipworth et al., ScientificReports 4, 3642 (2014); doi:10.1038/srep03642. For example, see FIG. 5of Lipworth. An illustration of coupled, multi-turn rectangular planarspiral inserts may be drawn from the Squid antenna implementations andinductive-coupling RFID tags.

Returning to FIG. 2, in an embodiment, the at least two artificiallystructured electromagnetic unit cells 322 includes at least twometamaterial unit cells. In an embodiment, a unit cell of the at leasttwo artificially structured electromagnetic unit cells includes anartificially structured metamaterial unit cell with a strong magneticresponse. In an embodiment, a unit cell of the at least two artificiallystructured electromagnetic unit cells includes an artificiallystructured, high inductance density metamaterial unit cells.

In an embodiment, the at least two artificially structuredelectromagnetic unit cells 322 include at least two periodicallyarranged, artificially structured electromagnetic unit cells. In anembodiment, the at least two artificially structured electromagneticunit cells include at least two artificially structured sub-wavelengthelectromagnetic unit cells. In an embodiment, the at least twoartificially structured electromagnetic unit cells respectively includea split ring resonator insertion optimized to generate a high inductancedensity. For example, see the split ring 324B of FIG. 3B. In anembodiment, the at least two artificially structured electromagneticunit cells respectively include two orthogonally oriented split ringresonator insertions optimized to generate a high inductance density. Inan embodiment, the at least two artificially structured electromagneticunit cells respectively include three orthogonally oriented split ringresonator insertions optimized to generate a high inductance density. Inan embodiment, the at least two artificially structured electromagneticunit cells respectively include a spiral insertion optimized to generatea high inductance density. In an embodiment, the spiral insertionincludes a rectangular or circular spiral insertion optimized togenerate a high inductance density. In an embodiment, a unit cell of theat least two artificially structured electromagnetic unit cells includesa conical helix or cylindrical helix insertion optimized to generate ahigh inductance density. For example, see the conical helix insertion324D of FIG. 3D. In an embodiment, a unit cell of the at least twoartificially structured electromagnetic unit cells includes twoorthogonally oriented conical helical insertions optimized to generate ahigh inductance density. In an embodiment, a unit cell of the at leasttwo artificially structured electromagnetic unit cells includes threeorthogonally oriented cylindrical helical insertions optimized togenerate a high inductance density. In an embodiment, a unit cell of theat least two artificially structured electromagnetic unit cells includesa pyramidal helical insertion optimized to generate a high inductancedensity. In an embodiment, the at least two artificially structuredelectromagnetic unit cells are configured to induce a B₁ magnetic fieldcomponent orthogonal to the z-axis. In an embodiment, the at least twoartificially structured electromagnetic unit cells are configured toinduce a first B₁ magnetic field component orthogonal to the z-axis anda second B₁ magnetic field component orthogonal to the first B₁ magneticfield component. In an embodiment, the at least two artificiallystructured electromagnetic unit cells are configured to induce magneticfield B₁ components in all three mutually orthogonal orientations.

In an embodiment, the artificially structured electromagnetic unit cells322 include a sub-wavelength arrangement of magnetic dipole unit cells.For example, the sub-wavelength arrangement may include unit cellshaving cellular dimensions of less than one-half of a wavelength. Forexample, the sub-wavelength arrangement may include unit cells havingcellular dimensions of less than one-quarter of a wavelength. Forexample, the sub-wavelength arrangement may include a deeplysub-wavelength arrangement. For example, the sub-wavelength arrangementmay include unit cells having cellular dimensions of less than one-tenthof a wavelength. In an embodiment, the unit cells are densely packed todeliver a relatively large magnetic field or a large magnetic flux. Inan embodiment, the artificially structured electromagnetic unit cellsinclude a sub-wavelength arrangement of magnetic multipole unit cells.In an embodiment, the artificially structured electromagnetic unit cellsinclude a deeply sub-wavelength arrangement of magnetic multipole unitcells.

In an embodiment, the array 320 is configured to generate amagnetic-field B₁ in the near-field region. In an embodiment, the atleast two unit cells 322 are configured to generate a pulse of a tunableradiofrequency magnetic field B₁ 328. In an embodiment, the tunableradiofrequency magnetic field B₁ includes a frequency, amplitude, orpolarization tunable radiofrequency magnetic field B₁. In an embodiment,the tunable radiofrequency magnetic field B₁ is tunable over a portionof the 10-300 MHz range. This frequency range is often used for magneticresonant imaging or nuclear magnetic resonant imaging. In an embodiment,there is no true lower bound on the frequency used for magnetic resonantimaging or nuclear magnetic resonant imaging. If the primary field B₀strength is low, the B₁ frequency may be correspondingly lower; anddetection efficiency is correspondingly lower. In an embodiment,resonant unit cells producing the magnetic field B are loaded withadditional capacitors in order to lower the resulting resonancefrequency below their natural, unloaded resonance frequency. The upperfrequency limit for the B₁ frequency results from high-frequency waveattenuation and electric field absorption in the body. Reducing totalelectric field absorption in the body allows use of higherradiofrequency magnetic fields B₁, enabling higher detection efficiency.

In an embodiment, the array 320 is configured to be coaxially disposedabout the z-axis 318. In an embodiment, the array includes an arcuateshape dimensioned to be mounted or positioned within at least a portionof the bore 316 of the magnetic resonant imaging or the nuclear magneticresonant device. In an embodiment, the arcuate shape is dimensioned tobe mounted or positioned around less than 180-degrees of thecircumference of the bore. In an embodiment, the arcuate shape isdimensioned to be mounted or positioned around 180-degrees or more ofthe circumference of the bore. In an embodiment, the shape isdimensioned to be mounted or positioned around less than 270-degrees ofthe circumference of the bore. In an embodiment, the array has acylindrical or an annular shape dimensioned to be mounted or positionedwithin the bore of the magnetic resonant imaging or the nuclear magneticresonant device. In an embodiment, the array includes two arcuate shapedportions, each dimensioned to be less than 180-degrees of thecircumference of the bore, and mounted or positioned facing each otheracross the z-axis. In an embodiment, the array includes two generallyplanar portions, each configured to be mounted or positioned facing theother across the z-axis.

In an embodiment, the at least two artificially structured unitelectromagnetic cells 322 are configured to generate a highly inductiveelectromagnetic near field 328. In an embodiment, the at least twoartificially structured unit electromagnetic cells are configured togenerate a magnetic field-dominant radiofrequency near-field whosemagnetic (B₁) and electric (E₁) field intensities are such that(B₁c)/E₁>1 (where “c” is the speed of light). In an embodiment, the atleast two artificially structured electromagnetic unit cells areconfigured to generate a magnetic field-dominant radiofrequencynear-field where (B₁c)/E₁>10. For example, this is equivalent to(H₁·Z₀)/E₁>10 (where Z₀ is the free-space impedance). In an embodiment,the at least two artificially structured electromagnetic unit cells areconfigured to generate a magnetic field B₁ that includes a gradientorientated transverse to the z-axis 318. In an embodiment, the at leasttwo artificially structured electromagnetic unit cells are configured togenerate a magnetic field B₁ that includes two orthogonal gradientsorientated transverse to the z-axis. In an embodiment, the pulse ofradiofrequency magnetic field B₁ is linearly polarized relative to thez-axis. In an embodiment, the pulse of radiofrequency magnetic field B₁is circularly polarized relative to the z-axis.

In an embodiment, the array 320 of at least two electromagnetic unitcells 322 is further configured to receive magnetic resonance signalsgenerated by magnetically active nuclei disposed in an examinationregion of a magnetic resonant imaging or a nuclear magnetic resonantdevice 300, and to generate a signal indicative thereof. In anembodiment, the radiofrequency electromagnetic wave conducting structure380 is configured to distribute a received pulse of radiofrequencyelectromagnetic waves to the at least two artificially structuredelectromagnetic unit cells.

In an embodiment, the radiofrequency electromagnetic wave conductingstructure 380 is configured to distribute a pulse of radiofrequencyelectromagnetic waves 392 received from a radiofrequency power amplifiercomponent of the magnetic resonant imaging or a nuclear magneticresonant device 300 to the at least two artificially structuredelectromagnetic unit cells 322. In an embodiment, the radiofrequencyelectromagnetic wave conducting structure includes a transmission line,a waveguide, or other field-confining structure allowing fieldpropagation along at least one of its dimensions. In an embodiment, thewaveguide includes a leaky waveguide, or another field-propagatingstructure with a partial field confinement. In an embodiment, theradiofrequency electromagnetic wave conducting structure includes aradiofrequency electrical conductor; for example, a high electricalconductivity wire.

In an embodiment, the pulse of radiofrequency electromagnetic waves 392includes pulses of radiofrequency electromagnetic waves. In anembodiment, the pulse of radiofrequency electromagnetic waves isgenerated in response to a pulse programmer component of the magneticresonant imaging or a nuclear magnetic resonant device 300. In anembodiment, the pulse of radiofrequency electromagnetic waves isgenerated by a radiofrequency oscillator component of the magneticresonant imaging or a nuclear magnetic resonant device. In anembodiment, the pulse of radiofrequency electromagnetic waves isgenerated by a radiofrequency synthesizer component of the magneticresonant imaging or a nuclear magnetic resonant device. In anembodiment, a frequency of the radiofrequency pulse is selectedresponsive to a resonate frequency of the at least two unit cells 322.In an embodiment, the radiofrequency pulse includes a shapedradiofrequency pulse. In an embodiment, the radiofrequency pulseincludes a tailored radiofrequency sinc pulse or tailored radiofrequencysinc pulses.

In an embodiment, each unit cell of at least two artificially structuredelectromagnetic unit cells 322 includes a radiofrequency electromagneticwave conducting component coupled with the radiofrequencyelectromagnetic wave conducting structure 380.

In an alternative embodiment, the at least two artificially structuredelectromagnetic unit cells 322 include at least two assemblages 1215 ofartificially structured electromagnetic unit cells 1220. For example,FIG. 12 illustrates an assemblage of the at least two assemblages ofartificially structured electromagnetic unit cells. Each assemblageincludes a first artificially structured electromagnetic unit cell(illustrated as first unit cells 1222.1 and 1222.2) configured togenerate the pulse of a radiofrequency magnetic field B₁, and a secondartificially structured electromagnetic unit cell (illustrated as secondunit cells 1224.1 and 1224.2) configured to generate a radiofrequencyelectric field E counteracting a non-vanishing electric field generatedby the first artificially structured electromagnetic unit cell. Thisassemblage decouples the strength of the radiofrequency magnetic fieldB₁ from the strength of the radiofrequency electric field E in a space,particularly in a near-field space.

FIG. 4 illustrates an example operational flow 400. After a startoperation, the operational flow includes a reception operation 410. Thereception operation includes receiving a pulse of radiofrequencyelectromagnetic waves from a radiofrequency signal generator orsynthesizer component of a magnetic resonant imaging or a nuclearmagnetic resonant device. In an embodiment, the reception operation maybe implemented using the radiofrequency electromagnetic wave conductingstructure 380 to receive the pulse 392 described in conjunction withFIG. 2. A dissemination operation 420 includes distributing the receivedpulse of radiofrequency electromagnetic waves as an incident pulse ofradiofrequency electromagnetic waves to at least two artificiallystructured electromagnetic unit cells of an array. In an embodiment, thedissemination operation may be implemented using the radiofrequencyelectromagnetic wave conducting structure 380 to distribute the pulse392 to the at least two artificially structured electromagnetic unitcells 322 of an array 320 described in conjunction with FIG. 2. Aconversion operation 430 includes transforming, using the at least twoartificially structured electromagnetic unit cells of the array, theincident pulse of radiofrequency electromagnetic waves into a pulse of aradiofrequency magnetic field B₁ orientated transverse to a quasistaticmagnetic field B₀ that is parallel to a z-axis of a bore of the magneticresonant imaging or the nuclear magnetic resonant device. The pulse ofthe radiofrequency magnetic field B₁ having a magnetic field intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within at least a portion of an examination regionlocated within the bore. In an embodiment, the conversion operation maybe implemented by the at least two artificially structuredelectromagnetic unit cells 322 of an array 320 described in conjunctionwith FIG. 2. The operational flow includes an end operation.

FIG. 5 illustrates an example apparatus 500. The apparatus includesmeans 510 for receiving a pulse of radiofrequency electromagnetic wavesfrom a radiofrequency signal generator or synthesizer component of amagnetic resonant imaging or a nuclear magnetic resonant device. Theapparatus includes means 520 for distributing the received pulse ofradiofrequency electromagnetic waves as an incident pulse ofradiofrequency electromagnetic waves to an artificially structured meansfor transforming radiofrequency electromagnetic waves. The apparatusincludes artificially structured means 530 for transforming the incidentpulse of radiofrequency electromagnetic waves into a pulse of aradiofrequency magnetic field B₁ orientated transverse to a quasistaticmagnetic field B₀ parallel to a z-axis of a bore of the magneticresonant imaging or the nuclear magnetic resonant device. The pulse ofthe radiofrequency magnetic field B₁ having a magnetic field intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within at least a portion of an examination regionlocated within the bore.

FIG. 6 illustrates an example apparatus 605 configured to generate aradiofrequency magnetic field B₁ in a magnetic resonant imaging or anuclear magnetic resonant device, for example, such as the magneticresonant imaging or a nuclear magnetic resonant device 300 described inconjunction with the environment 200 in FIGS. 1 and 2. The apparatusincludes an array 610 of at least two groups 620 of at least twoartificially structured electromagnetic unit cells 624. The at least twogroups are illustrated by a group 622.1, a group 622.2, a group 622.3, agroup 622.4, and a group 622.5. Each group of the at least two groups isconfigured to be respectively linearly arranged with respect to thez-axis 318 of the bore 316 of the magnetic resonant imaging or a nuclearmagnetic resonant device. An embodiment of at least two artificiallystructured electromagnetic unit cells 624 is illustrated as a 2×2arrangement of artificially structured electromagnetic unit cells. In anembodiment for example, a group of the at least two artificiallystructured electromagnetic unit cells 624 may include an arrangementunit cells of hundreds or thousands of unit cells in a circumferentialdirection around the group, and tens or hundreds of unit cells across awidth of the group. The artificial structure of unit cells, includinginclusions, and the arrangement of the unit cells may be selected ordesigned by one skilled in the art responsive to the particular designrequirements and materials available. For example, FIG. 3 andaccompanying description illustrate several artificial structures ofunit cells. Each group of the at least two groups 620 of artificiallystructured electromagnetic unit cells 624 is configured to transform anincident pulse 692 of radiofrequency electromagnetic waves into a pulseof radiofrequency magnetic field B₁ orientated transverse to a segmentof the z-axis 318 (hereafter “transverse segment”) and spatiallyproximate to the group.

For example, the group 622.1 of unit cells is configured to transformthe incident pulse into a pulse of radiofrequency magnetic field B_(1.1)orientated transverse to a segment of the z-axis, and having asubstantial portion of the radiofrequency magnetic field B_(1.1)intensity proximate to the group 622.1. While ultimately a function ofdesign and materials selected for the array, in an example operationalembodiment of the array 610, the intensity of the radiofrequencymagnetic field B_(1.1) proximate to the group 622.1 may be at least fivetimes the intensity of the radiofrequency magnetic field B_(1.5)proximate to the group 622.5. Similarly, in another example operationalembodiment, the intensity of the radiofrequency magnetic field B_(1.3)proximate to the group 622.3 may be at least two times the intensity ofthe radiofrequency magnetic fields B_(1.1) and B_(1.5) respectivelyproximate to the groups 622.1 and 622.5.

The apparatus 605 includes a radiofrequency electromagnetic waveconducting structure 680 configured to selectively distribute a receivedpulse of radiofrequency electromagnetic waves 692 to a group of the atleast two groups 620. In an embodiment, the selectively distribute isresponsive to a control signal 673 generated by a controller 672.

In an embodiment, each group of the at least two groups 620 ofartificially structured electromagnetic unit cells 624 is configured totransform an incident pulse of radiofrequency electromagnetic waves 692into a pulse of radiofrequency magnetic field B₁ having a magnetic fieldintensity sufficient to excite a detectable magnetic resonance inmagnetically active nuclei located within the transverse segmentspatially proximate to the group.

In an embodiment, a group of the at least two groups 620 has an annularshape. In an embodiment, each group of the at least two groups has anannular shape. In an embodiment, each group of the at least two groupsis configured to be coaxially arranged about the z-axis 318. In anembodiment, each group of the at least two groups is configured to becoaxially arranged and sequentially positioned about the z-axis. In anembodiment, each group of the at least two groups is configured to besequentially positioned in a respective plane transverse to the z-axis.

In an embodiment, each group of the at least two groups 620 isconfigured to transform an incident pulse 692 of radiofrequencyelectromagnetic waves into a pulse of radiofrequency magnetic field B₁orientated transverse to a segment of the quasistatic magnetic field B₀parallel to the z-axis 318 and spatially proximate to the group.

In an embodiment, the at least two groups 620 each include at least tworandomly accessible groups of at least two artificially structuredelectromagnetic unit cells 625. In an embodiment, the at least twoartificially structured electromagnetic unit cells of a group of the atleast two randomly accessible groups include at least two electronicallycontrollable artificially structured electromagnetic unit cells. In anembodiment, the at least two artificially structured electromagneticunit cells of a group of the at least two randomly accessible groupsinclude at least two active, artificially structured electromagneticunit cells. For example, active, artificially structured electromagneticunit cells may include active lumped element unit cells. For example,active, artificially structured electromagnetic unit cells may includeelectronically controllable or switchable unit cells. In an embodiment,the at least two artificially structured electromagnetic unit cells of agroup include at least two powered, artificially structuredelectromagnetic unit cells. An example of a powered, artificiallystructured electromagnetic unit cell is described in Y. Yuan, et al.,Zero loss magnetic metamaterials using powered active unit cells, Vol.17, No. 18 Optics Express 13136 (Aug. 31, 2009). In an embodiment, theat least two artificially structured electromagnetic unit cells includeat least two self-resonant, artificially structured electromagnetic unitcells. In an embodiment, the at least two artificially structuredelectromagnetic unit cells include at least twoelectrically-controllable, artificially structured electromagnetic unitcells. In an embodiment, the at least two artificially structuredelectromagnetic unit cells of a group include at least two randomlyaccessible, artificially structured electromagnetic unit cells. In anembodiment, the at least two artificially structured electromagneticunit cells of a group are configured to generate a pulse of a tunableradiofrequency magnetic field B₁. In an embodiment, tunableradiofrequency magnetic field includes tunable over a portion of the10-300 MHz range typically used by a magnetic resonant imaging or anuclear magnetic resonant devices 300.

In an embodiment, a first group of the at least two groups 620 includesat least two artificially structured unit electromagnetic cells 624configured to generate a magnetic field-dominant radiofrequencynear-field whose magnetic and electric field intensities are such that(B₁c)/E₁>1. A second group of the at least two groups includes at leasttwo artificially structured unit electromagnetic cells configured togenerate an electric field counteracting a non-vanishing electric fieldgenerated by the first group of artificially structured electromagneticunit cells.

In an embodiment, the at least two artificially structuredelectromagnetic unit cells 624 of each group of at least two groups 620include at least two assemblages of artificially structuredelectromagnetic unit cells. For example, FIG. 12 illustrates anassemblage 1215 of the at least two assemblages of artificiallystructured electromagnetic unit cells. In this embodiment, eachassemblage of the at least two assemblages of artificially structuredelectromagnetic unit cells includes (i) a first artificially structuredelectromagnetic unit cell (illustrated as the first unit cells 1222.1and 1222.2) configured to transform an incident pulse of radiofrequencyelectromagnetic waves into a pulse of the radiofrequency magnetic fieldB₁ and (ii) a second artificially structured electromagnetic unit cell(illustrated as the second unit cells 1224.1 and 1224.2) configured totransform the incident pulse of radiofrequency electromagnetic wavesinto an electric field E counteracting a non-vanishing electric fieldcomponent generated by the first artificially structured electromagneticunit cell.

FIG. 7 illustrates an example operational flow. After a start operation,the operational flow includes a reception operation 710. The receptionoperation includes receiving a pulse of radiofrequency electromagneticwaves from a radiofrequency signal generator or signal synthesizercomponent of a magnetic resonant imaging or a nuclear magnetic resonantdevice. In an embodiment, the reception operation may be implemented bythe radiofrequency electromagnetic wave conducting structure 680receiving the pulse 692 as described in conjunction with FIG. 6. Adissemination operation 720 includes distributing the received pulse ofradiofrequency electromagnetic waves as an incident pulse ofradiofrequency electromagnetic waves to a selected group of an array ofat least two groups of at least two artificially structuredelectromagnetic unit cells. In an embodiment, the disseminationoperation may be implemented by using a respective radiofrequencyelectromagnetic wave conducting sub-structure coupled to each group ofthe at least two groups 620 of the artificially structuredelectromagnetic unit cells 624, illustrated in FIG. 6 as sub-structures682.1-682.5. A conversion operation 730 includes transforming, using theat least two artificially structured electromagnetic unit cells of theselected group, the incident pulse of radiofrequency electromagneticwaves into a localized pulse of a radiofrequency magnetic field B₁orientated transverse to a z-axis of a bore of the magnetic resonantimaging or the nuclear magnetic resonant device. In an embodiment, theconversion operation may be implemented using the at least twoartificially structured electromagnetic unit cells of the selected groupof the at least two groups 620, such as for example the group 622.3described in conjunction with FIG. 6. The operational flow includes anend operation.

In an embodiment of the conversion operation 730, the localized pulse740 of the radiofrequency magnetic field B₁ has a magnetic fieldintensity sufficient to excite a detectable magnetic resonance inmagnetically active nuclei located within at least a portion of thetransverse segment of an examination region located within the bore. Inan embodiment of the conversion operation, the transforming includestransforming an incident pulse of radiofrequency electromagnetic wavesinto a pulse of radiofrequency magnetic field B₁ transverse to a segmentof the quasistatic magnetic field B₀ parallel to the z-axis andspatially proximate to the group. In an embodiment, the operational flowincludes selecting the group of the at least two groups of at least twoartificially structured electromagnetic unit cells in response to dataindicative of a location along the z-axis of a transverse slice selectedfor examination.

Returning to FIG. 6: FIG. 6 also illustrates a system 602 that includesan alternative embodiment of the example system 602 and apparatus 605configured to generate a radiofrequency magnetic field B₁ in a magneticresonant imaging or a nuclear magnetic resonant device, for example,such as the magnetic resonant imaging or a nuclear magnetic resonantdevice 300 described in conjunction with the environment 200 in FIG. 1.The system includes an array 610 of at least two groups 620 of at leasttwo artificially structured electromagnetic unit cells 624. Each groupof the at least two groups configured to be respectively linearlyarranged with respect to the z-axis 318 of the bore 316 of a magneticresonant imaging or a nuclear magnetic resonant device. Each group ofthe at least two artificially structured electromagnetic unit cells isrespectively configured to transform incident pulses 692 ofradiofrequency electromagnetic waves into pulses of radiofrequencymagnetic field B₁ orientated transverse to a segment of the z-axis 318(hereafter “transverse segment) and spatially proximate to the group.

The system 602 includes a radiofrequency electromagnetic wave conductingstructure 680 configured to distribute the pulses 692 of radiofrequencyelectromagnetic waves as the incident pulses of the radiofrequencyelectromagnetic waves to a selectable group of the at least two groups620 in response to a B₁ localization control signal 673. The systemincludes a control circuit 672 configured to generate the B₁localization control signal defining a respective power distribution ofa particular incident pulse of radiofrequency electromagnetic waves toeach group of the at least two groups. The respective power distributioncollectively defining a particular pulse of radiofrequency magneticfield B₁ localized to a selected arbitrary examination segmenttransverse to the z-axis 318 and within an examination region of thebore 316. The localized magnetic field B₁ having an intensity sufficientto excite a detectable magnetic resonance in magnetically active nucleilocated within the selected arbitrary examination segment.

In an embodiment, each group of the at least two groups 620 isrespectively individually accessible or controllable independent oftheir respective location or sequence in the array 610. For example, anygroup of unit cells may be accessed or controlled as about as easily andefficiently as any other group of unit cells in the array, no matter howmany other groups there are in the array. In an embodiment, individuallyaccessible or controllable includes an ability to access or control anygroup of at least two unit cells in the array independent of itsposition, size, characteristic, etc. in the array. In an embodiment,each group of the at least two groups is respectively electronicallyaccessible or controllable independent of the other groups. In anembodiment, the selected arbitrary examination segment includes aselected cylindrical arbitrary transverse segment having a centerline onthe z-axis 318. In an embodiment, the selected arbitrary examinationsegment includes a selected arbitrary segment transverse to and having athickness relative to the z-axis. In an embodiment, the selectedarbitrary examination segment includes at least one transverse segmentspatially proximate to a group of the at least two groups. In anembodiment, the selected arbitrary examination segment includes withinits z-axis boundaries a transverse slice of the examination regionselected for examination. In an embodiment, the localized pulse has amagnetic field intensity sufficient to excite a detectable magneticresonance in magnetically active nuclei located within the transverseslice of the examination region.

In an embodiment, the system 602 includes a receiver 674 configured toreceive data indicative of a location along the z-axis 318 of thetransverse slice selected for examination. In an embodiment, the controlcircuit 672 is configured to select the arbitrary examination segmentresponsive to the data indicative of the location of the slice along thez-axis.

In an embodiment, the localized pulse of the radiofrequency magneticfield B₁ produces a quasi-focused radiofrequency magnetic field B₁localized to include the selected arbitrary examination segment. In anembodiment, the localized pulse of the radiofrequency magnetic field B₁produces a near-field magnetic field fan beam pattern localized toinclude the selected arbitrary examination segment. In an embodiment,the localized pulse has a magnetic field intensity sufficient to excitea detectable magnetic resonance in magnetically active nuclei in apotential examination subject located in the selected arbitraryexamination segment. For example, a potential examination subject mayinclude a human being, an animal subject, or an inanimate object.

Advantages of the example system 602 and apparatus 605 include producinglower electric field densities (and correspondingly SAR) than would begenerated by a “standard”, magnetic field B₁ generator of a traditionalmagnetic resonant imaging or a nuclear magnetic resonant device,particularly in the examination slice itself. The example system andapparatus produce an average E/(Bc) ratio in the examination slice thatis less than what it would be inside a simple solenoidal generator ofthe same size operating at the same frequency and producing the sameaverage B field intensity of a traditional magnetic resonant imaging ora nuclear magnetic resonant device.

In an embodiment, the localized pulse of the radiofrequency magneticfield B₁ includes a first electric field intensity in the selectedarbitrary examination segment and includes a second electric fieldintensity in another arbitrary transverse segment of the examinationregion, the second electric field intensity less than the first electricfield intensity. For example, the group 622.3 may create a localizedpulse of the radiofrequency magnetic field B_(1.3) and an accompanyingfirst electric field intensity in the selected arbitrary examinationsegment proximate to the group 622.4, and an accompanying secondelectric field intensity in another arbitrary transverse segmentproximate to the group 622.2. In an embodiment, the other arbitrarytransverse segment abuts the selected arbitrary examination segment. Inan embodiment, the other arbitrary transverse segment has a z-axisthickness along the z-axis equal to or greater than the selectedarbitrary transverse segment. In an embodiment, the localized pulse ofthe radiofrequency magnetic field B₁ includes a first radiofrequencyelectric field intensity in the selected arbitrary examination segmentand includes a second radiofrequency electric field intensity in asecond arbitrary transverse segment of the examination region. Thesecond radiofrequency electric field intensity is less than the firstradiofrequency electric field intensity.

The formula for computing energy density or energy per unit volume

$\frac{U}{V}$

of an electrostatic or quasistatic field is:

${u_{e} = {\frac{1}{2}ɛ_{0}{E}^{2}}},{{Joules}\text{/}{M^{3}.}}$

In human tissue ∈₀ is replaced with ∈′, the real part of the dielectricpermittivity of the tissue. The formula for the dissipation rate densityis similar; it is the same as above, but ∈′ is replaced with theelectrical conductivity σ: Q=

$\frac{1}{2}\sigma {{\overset{->}{E}}^{2}.}$

The specific absorption rate (measured in W/kg) is defined as thedissipation rate density (measured in W/m3) divided by density.

In an embodiment, the second arbitrary transverse segment abuts theselected arbitrary examination segment. In an embodiment, the secondarbitrary transverse segment has a z-axis thickness equal to or greaterthan the selected arbitrary examination segment. In an embodiment, thesecond radiofrequency electric field intensity is less than 66% of thefirst radiofrequency electric field intensity. In an embodiment, thesecond electric field intensity is less than 50% of the first electricfield intensity. In an embodiment, the second electric field intensityis less than 33% of the first electric field intensity.

In an embodiment, the respective power distribution further collectivelydefining a particular pulse of radiofrequency magnetic field B₁producing a minimized specific absorption rate (SAR) in the selectedarbitrary examination segment. In an embodiment, the defined particularpulse of radiofrequency magnetic field B₁ is configured in response to amodel-based estimation of the localized pulse respective powerdistribution providing a minimized SAR. In an embodiment, themodel-based estimation is optimized responsive to a set of configurablerules. In an embodiment, the model-based estimation of a respectivepower distribution is selected from a best available distribution schemefrom at least two available distribution schemes. In an embodiment, themodel-based estimation of a respective power distribution is retrievedfrom a computer readable storage medium. In an embodiment, therespective power distribution is empirical-determined on the fly. In anembodiment, the respective power distribution is responsive to acontemporaneously-determined distribution of a radiofrequency magneticfield B₁ localized to the selected arbitrary examination segment withthe minimized SAR. In an embodiment, the contemporaneously-determineddistribution is responsive to data contemporaneously received from atleast one radiofrequency electric field sensor. In an embodiment, thecontemporaneously-determined distribution is responsive to a set ofrules. In an embodiment, the respective power distribution is selectedresponsive to a matrix factorization, or a matrix decomposition basedoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a gradient descent basedoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a singular value decompositionoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a principle component analysisbased optimization technique. In an embodiment, the respective powerdistribution is selected responsive to a trial and error, or a bruteforce based optimization technique. In an embodiment, the respectivepower distribution is selected responsive to a best available respectivepower distribution.

In an embodiment, the localized pulse of the radiofrequency magneticfield B₁ includes (i) a first radiofrequency electric field intensity inthe selected arbitrary examination segment, (ii) a second radiofrequencyelectric field intensity in a second arbitrary transverse segment of theexamination region abutting the selected arbitrary transverse segment,and (iii) a third radiofrequency electric field intensity in a thirdarbitrary transverse segment of the examination region abutting theselected arbitrary transverse segment and positioned opposite to thesecond arbitrary transverse segment. In this embodiment, the second andthird radiofrequency electric field intensities are each less than thefirst radiofrequency electric field intensity. In an embodiment, thethird arbitrary transverse segment has a z-axis thickness equal to orgreater than the selected arbitrary examination segment. In anembodiment, the second radiofrequency electric field intensity is lessthan 66% of the first radiofrequency electric field intensity. In anembodiment, the second electric field intensity is less than 50% of thefirst electric field intensity. In an embodiment, the second electricfield intensity is less than 33% of the first electric field intensity.

In an embodiment, the localized pulse of the radiofrequency magneticfield B₁ is configured to produce a first specific absorption rate (SAR)(W/kg) in an examination subject located in the selected arbitraryexamination segment, and to produce a second SAR in another arbitrarytransverse segment of the examination region, the second SAR less thanthe first SAR. In an embodiment, the second SAR is less than 66% of thefirst SAR. In an embodiment, the second SAR is less than 50% of thefirst SAR. In an embodiment, the second SAR is less than 33% of thefirst SAR. In an embodiment, the radiofrequency magnetic field B₁includes a pulse of tunable radiofrequency magnetic field B₁.

In an embodiment, the respective power distribution further includes arespective power distribution collectively defining a particular pulseof radiofrequency magnetic field B₁ producing a minimized specificabsorption rate (SAR) in the selected arbitrary examination segment. Inan embodiment, the defined particular pulse of radiofrequency magneticfield B₁ is configured in response to a model-based estimation of thelocalized pulse respective power distribution providing a minimized SAR.In an embodiment, the model-based estimation is optimized responsive toa set of configurable rules. In an embodiment, the model-basedestimation of a respective power distribution is selected from a bestavailable distribution scheme from at least two available distributionschemes. In an embodiment, the model-based estimation of a respectivepower distribution is retrieved from a computer readable storage medium.In an embodiment, the respective power distribution isempirical-determined on the fly. In an embodiment, the respective powerdistribution is responsive to a contemporaneously-determineddistribution of a radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment with the minimized SAR. In anembodiment, the contemporaneously-determined distribution is responsiveto data contemporaneously received from at least one radiofrequencyelectric field sensor. In an embodiment, thecontemporaneously-determined distribution is responsive to a set ofrules. In an embodiment, the respective power distribution is selectedresponsive to a matrix factorization, or a matrix decomposition basedoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a gradient descent basedoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a singular value decompositionoptimization technique. In an embodiment, the respective powerdistribution is selected responsive to a principle component analysisbased optimization technique. In an embodiment, the respective powerdistribution is selected responsive to a trial and error, or a bruteforce based optimization technique. In an embodiment, the respectivepower distribution is selected responsive to a best available respectivepower distribution.

In an embodiment, the respective power distribution further includes arespective power distribution collectively defining a particular pulseof radiofrequency magnetic field B₁ producing a selected ratio of thetotal specific absorption rate (SAR) produced in an examination subjectover an averaged total SAR produced in the selected arbitraryexamination segment. In an embodiment, the selected ratio includes aselected minimized ratio. In an embodiment, the selected ratio isselected in response to a model-based estimation of the total specificabsorption rate (SAR) produced in an examination subject over anaveraged total SAR produced in the selected arbitrary examinationsegment. In an embodiment, the selected ratio is selected responsive toa set of rules. In an embodiment, the selected ratio is selectedresponsive to a matrix factorization, or a matrix decomposition basedoptimization technique. In an embodiment, the selected ratio is selectedresponsive to a gradient descent based optimization technique. In anembodiment, the selected ratio is selected responsive to a singularvalue decomposition optimization technique.

In an embodiment, the array 620 of at least two groups 620 iselectronically controllable to initiate a generation of the pulse of theradiofrequency magnetic field B₁ to the selected arbitrary segment.

In an embodiment, the radiofrequency electromagnetic wave conductingstructure 680 is configured to receive the pulse 692 of radiofrequencyelectromagnetic waves from a radiofrequency power amplifier component ofthe magnetic resonant imaging or a nuclear magnetic resonant device 300.See FIGS. 1 and 2. In an embodiment, the radiofrequency electromagneticwave conducting structure includes an electronically controllable switch686 responsive to the B₁ localization control signal 673 and coupledbetween a primary portion of the radiofrequency electromagnetic waveconducting structure and a secondary portion 682 of the radiofrequencyelectromagnetic wave conducting structure. The secondary portion iscoupled to at least one group of the at least two groups 620. In anembodiment, the secondary portion of the radiofrequency electromagneticwave conducting structure includes a respective radiofrequencyelectromagnetic wave conducting sub-structure coupled to each group ofthe at least two groups of artificially structured electromagnetic unitcells. For example, a wave conducting sub-structure portion 682.1 iscoupled between the conducting structure 680 and the group 622.1.Similarly, wave conducting sub-structure portions 682.2-682.5 arerespectively coupled between the primary portion of the radiofrequencyelectromagnetic wave conducting structure and the groups 622.2-622.5.

In an embodiment, the respective power distribution defines a pulse ofradiofrequency magnetic field B₁ orientated transverse to the z-axis 318and within the examination region of the bore 316. In an embodiment, theselected arbitrary examination segment includes within its z-axisboundaries a transverse slice selected for examination. For example,during an imaging procedure, the selected examination segment is steppedor moved along the z-axis. In this example, the localized pulse of theradiofrequency magnetic field B₁ is selectively stepped or moved alongthe z-axis by selecting which group or groups of at least two unit cellsreceive the distribution of the pulse 692 of radiofrequencyelectromagnetic waves.

In an embodiment, the localized pulse has a magnetic field intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within the transverse slice of selected arbitraryexamination segment.

In an embodiment, the respective power distribution defines a particularpulse of radiofrequency magnetic field B₁ localized to the selectedarbitrary examination segment and having a substantially uniformmagnetic field intensity. In an embodiment, the substantially uniformmagnetic field intensity includes less than an approximately one-tenthof a percent variation in the radiofrequency magnetic field B₁ intensityacross the selected arbitrary examination segment. In an embodiment, thesubstantially uniform magnetic field intensity includes less than anapproximately one percent variation in the radiofrequency magnetic fieldB₁ intensity across the selected arbitrary examination segment. In anembodiment, the substantially uniform magnetic field intensity includesless than an approximately ten percent variation in the radiofrequencymagnetic field B₁ intensity across the selected arbitrary examinationsegment. In an embodiment, the substantially uniform magnetic fieldintensity includes a variation in the radiofrequency magnetic field B₁intensity across the selected arbitrary examination segment by a factorof less than two. In an embodiment, the substantially uniform magneticfield intensity includes a variation in the radiofrequency magneticfield B₁ intensity across the selected arbitrary examination segment bya factor of less than ten.

In an embodiment, the respective power distribution includes amodel-based estimation of a respective power distribution providing apulse of radiofrequency magnetic field B₁ localized to the selectedarbitrary examination segment. In an embodiment, the model-basedestimation is optimized responsive to a set of rules. For example, therules may be configurable. In an embodiment, the model-based estimationof a respective power distribution is selected from a best availabledistribution scheme from at least two available distribution schemes. Inan embodiment, the model-based estimation of a respective powerdistribution is retrieved from a computer readable storage medium. In anembodiment, the respective power distribution is empirically-determinedon the fly. In an embodiment, the model-based estimation of a respectivepower distribution is responsive to a contemporaneously-determineddistribution of a radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment. In an embodiment, themodel-based estimation of a respective power distribution is responsiveto data contemporaneously received from at least one radiofrequencymagnetic field sensor positioned within the bore. In an embodiment, themodel-based estimation of a respective power distribution is responsiveto a detected magnetic resonance in magnetically active nuclei locatedwithin at least a portion of the examination region. For example, thedetected magnetic resonance may be from a previous localized pulse. Forexample, if the pulse amplitude is not strong enough to detect magneticresonance, or is too strong, the amplitude of pulse may be changed byaltering the distribution.

In an embodiment, the respective power distribution defines an optimizedpulse of the radiofrequency magnetic field B₁ localized to the selectedarbitrary examination segment. In an embodiment, the optimized pulse isselected responsive to a set of rules. In an embodiment, the optimizedpulse is selected responsive to a matrix factorization, or a matrixdecomposition based optimization technique. In an embodiment, theoptimized pulse is selected responsive to a gradient descent basedoptimization technique. In an embodiment, the optimized pulse isselected responsive to a singular value decomposition optimizationtechnique. In an embodiment, the optimized pulse is selected responsiveto a principle component analysis based optimization technique. In anembodiment, the optimized pulse is selected responsive to a trial anderror, or a brute force based optimization technique. In an embodiment,the optimized pulse is selected responsive to a best availablerespective power distribution. In an embodiment, the optimized pulseincludes a pulse of radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment and having magnetic fieldintensity sufficient to excite a detectable magnetic resonance inmagnetically active nuclei located within the selected arbitraryexamination segment. The optimized pulse is subject to a constraintlimiting the electric field intensity within the transverse segment toless than a preselected value.

In an embodiment, the unit cells 624 of each group of the at least twogroups 620 include at least two electronically controllable,artificially structured electromagnetic unit cells. In an embodiment,the unit cells of each group of the at least two groups include at leasttwo electronically controllable, randomly accessible, artificiallystructured electromagnetic unit cells. For example, the unit cells maybe randomly accessible individually or in groups.

In an embodiment, the respective power distribution defined by thecontrol signal 673 further includes a gradient component of theradiofrequency magnetic field B₁ intensity orthogonal to the z-axis 318.For example, an orthogonal variation in the B₁ field intensity may becreated to respond to a thickness variation in a subject being imaged.The gradient component may be implemented by electronically controllableunit cells within a group of the at least two groups 620. In anembodiment, the gradient component includes a gradient component in tworespective directions orthogonal to the z-axis. In an embodiment, thesystem 602 includes a unit cell controller (not shown) configured toelectronically control the at least two electronically controllable,artificially structured electromagnetic unit cells 624 of each group ofthe at least two groups 620 in response to the gradient component of thecontrol signal.

In an embodiment, the at least two artificially structuredelectromagnetic unit cells 624 of each group of the at least two groups620 include a single layer of at least two artificially structuredelectromagnetic unit cells configured to generate a magnetic fieldcomponent orthogonal to the z-axis. In an embodiment, the at least twoartificially structured electromagnetic unit cells of each group of theat least two groups include a first layer of at least two artificiallystructured electromagnetic unit cells and a second layer of at least twoartificially structured electromagnetic unit cells, the unit cells ofthe first layer configured to generate a magnetic field componentorthogonal to the z-axis, and the unit cells of the second layerconfigured to generate a magnetic field component orthogonal to themagnetic field component of the first layer of unit cells. In anembodiment, the at least two artificially structured electromagneticunit cells of each group of the at least two groups includes a firstlayer of at least two artificially structured electromagnetic unitcells, a second layer of at least two artificially structuredelectromagnetic unit cells, and a third layer of at least twoartificially structured electromagnetic unit cells, the three layers ofunit cells in combination configured to generate magnetic fieldcomponents in all three mutually orthogonal orientations.

In an embodiment, the at least two artificially structuredelectromagnetic unit cells 624 of each group of the at least two groups620 include a single layer of the at least two artificially structuredelectromagnetic unit cells that in combination are configured togenerate a radiofrequency magnetic field B₁ in two orthogonaldirections. In an embodiment, the at least two artificially structuredelectromagnetic unit cells of each group of the at least two groupsinclude a single layer of the at least two artificially structuredelectromagnetic unit cells that in combination are configured togenerate a radiofrequency magnetic field B₁ in all three mutuallyorthogonal orientations.

FIG. 8 illustrates an example operational flow 800. After a startoperation, the operational flow includes a reception operation 810. Thereception operation includes receiving a pulse of radiofrequencyelectromagnetic waves from a radiofrequency signal generator or signalsynthesizer component of a magnetic resonant imaging or a nuclearmagnetic resonant device. In an embodiment, the reception operation maybe implemented using the radiofrequency electromagnetic wave conductingstructure 680 to receive the pulse 692 as described in conjunction withFIG. 6. A localization operation 820 includes generating a B₁localization control signal defining a respective distribution of thepulse of radiofrequency electromagnetic waves to each group of the atleast two selectable groups of at least two artificially structuredelectromagnetic unit cells. Each group of the at least two selectablegroups configured to be respectively linearly arranged with respect to az-axis of a bore of the magnetic resonant imaging or the nuclearmagnetic resonant device. The respective power distribution collectivelydefining a pulse of radiofrequency magnetic field B₁ localized to aselected arbitrary examination segment transverse to the z-axis andwithin an examination region of the bore. In an embodiment, thelocalization operation may be implemented using the controller 672described in conjunction with FIG. 6. A dissemination operation 830includes distributing the received pulse of radiofrequencyelectromagnetic waves as an incident pulse of radiofrequencyelectromagnetic waves to a group of the at least two selectable groupsin accord with the B₁ localization control signal. In an embodiment, thedissemination operation may be implemented using the electromagneticwave conducting structure 680, the electronically controllable switch686, and the wave conducting sub-structure portions 682.1-682.5described in conjunction with FIG. 6. A conversion operation 840includes transforming, using the at least two artificially structuredelectromagnetic unit cells of the group, the incident pulse ofradiofrequency electromagnetic waves into a localized pulse of aradiofrequency magnetic field B₁ orientated transverse to the selectedarbitrary examination segment. The localized pulse having an intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within the selected arbitrary examination segment.In an embodiment, the conversion operation may be implemented by the atleast two artificially structured electromagnetic unit cells 624 of agroup of the at least two groups 620 described in conjunction with FIG.6. The operational flow includes an end operation.

In an embodiment, the operational flow 800 may include at least oneadditional operation. The at least one additional operation may includeselecting the arbitrary examination segment responsive to dataindicative of a location of a slice along the z-axis a transverseselected for examination.

FIG. 9 illustrates a system 902 that includes an embodiment of anexample apparatus 905 configured to generate a radiofrequency magneticfield B₁ in a magnetic resonant imaging or a nuclear magnetic resonantdevice, for example, such as the magnetic resonant imaging or a nuclearmagnetic resonant device described in conjunction with the environment200 in FIG. 1. The system includes an array 910 of at least two groups920 of at least two artificially structured electromagnetic unit cells924. Each group of the at least two groups is configured to besequentially positioned in a respective plane transverse to the z-axis318 of the bore 316 of a magnetic resonant imaging or a nuclear magneticresonant device. Each group of at least two groups includes a respectiveelectronically controllable, radiofrequency amplifier 960 (illustratedby amplifiers 960.1-960.5) switchable between an off-state and anon-state in response to a received B₁ localization control signal 973,and configured in the on-state to pass-through or amplify a receivedpulse of radiofrequency electromagnetic waves 992. For example, theelectronically controllable, radiofrequency amplifier associated with agroup 922.1 is illustrated by an electronically controllable,radiofrequency amplifier 960.1 coupled between a primary radiofrequencyelectromagnetic wave conducting structure 980 and a secondaryradiofrequency electromagnetic wave conducting structure 982.1. Theelectronically controllable, radiofrequency amplifiers associated withgroups 922.2-922.5 are similarly illustrated in FIG. 9. Each group of atleast two groups includes a respective secondary radiofrequencyelectromagnetic wave conducting structure configured to deliver anamplified pulse of radiofrequency electromagnetic waves to the at leasttwo artificially structured electromagnetic unit cells of the group asan incident amplified pulse of radiofrequency electromagnetic waves. Therespective secondary radiofrequency electromagnetic wave conductingstructures are schematically illustrated as secondary radiofrequencyelectromagnetic wave conducting structures 982.1-982.5. In anembodiment, the respective secondary radiofrequency electromagnetic waveconducting structures will form structures wrapping each group of the atleast two groups.

The at least two artificially structured electromagnetic unit cells 924of each group of the at least two groups 920 are respectively configuredto transform the delivered incident amplified pulse of radiofrequencyelectromagnetic waves into a pulse of radiofrequency magnetic field B₁orientated transverse to a segment of the z-axis 318 (hereafter“transverse segment”) and spatially proximate to the group. The at leasttwo artificially structured electromagnetic unit cells 924 areillustrated as a 2×2 arrangement of artificially structuredelectromagnetic unit cells. In an embodiment for example, a group of theat least two artificially structured electromagnetic unit cells 924 mayinclude an arrangement of unit cells of hundreds or thousands of unitcells in a circumference of the group, and tens or hundreds of unitcells over a width of the group. The artificial structure of unit cells,including inclusions, may be selected or designed by one skilled in theart responsive to the particular design requirements and materialsavailable. For example, FIG. 3 and accompanying description illustrateseveral artificial structures of unit cells.

The system 905 includes a control circuit 972 configured to select anarbitrary examination segment transverse to the z-axis 318 in responseto data indicative of a transverse slice selected for examination. Thecontrol circuit is configured to generate the B₁ localization controlsignal 673 defining an amplification state assigned to each group of theat least two groups 920. The amplification states collectively defininga pulse of radiofrequency magnetic field B₁ localized to the selectedarbitrary examination segment and having magnetic field intensitysufficient to excite a detectable magnetic resonance in magneticallyactive nuclei located within the selected arbitrary examination segment.

In an embodiment of the system 905, each radiofrequency amplifier 960 ofeach group of the at least two groups 920 is electronically switchablebetween an on-state and off-state. In an embodiment, each radiofrequencyamplifier of each group of the at least two groups includes anelectronically controllable variable gain amplifier. In an embodiment,the B₁ control signal 973 includes an amplification parameter assignedto a group of the at least two groups. In an embodiment, each group ofthe at least two groups includes an electronically controllableradiofrequency amplifier and an electronically controllable phaseshifter or variable phase delay lines. In an embodiment, the pulse ofradiofrequency electromagnetic waves 992 is received from aradiofrequency signal generator or synthesizer component of the magneticresonant imaging or a nuclear magnetic resonant device 300. In anembodiment, the data includes data indicative of a location along thez-axis 318 of the transverse slice selected for examination. In anembodiment, the defined pulse of radiofrequency magnetic field B₁localized to the selected arbitrary examination segment includes amagnetic field having intensity sufficient to excite a detectablemagnetic resonance in magnetically active nuclei located within theselected arbitrary segment.

In an embodiment, the amplification states collectively define anoptimized pulse of the radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment. In an embodiment, the optimizedpulse is selected responsive to a set of configurable rules. In anembodiment, the optimized pulse is selected responsive to a matrixfactorization, or a matrix decomposition based optimization technique.In an embodiment, the optimized pulse includes a pulse of radiofrequencymagnetic field B₁ localized to the selected arbitrary examinationsegment and having a magnetic field intensity sufficient to excite adetectable magnetic resonance in magnetically active nuclei locatedwithin the selected arbitrary examination segment. The optimized pulseis subject to a constraint limiting the electric field intensity withinthe selected arbitrary examination segment to less than a preselectedvalue.

In an embodiment of the system 905, the localized pulse of theradiofrequency magnetic field B₁ includes a first electric fieldintensity in the selected arbitrary examination segment and includes asecond electric field intensity in another arbitrary transverse segmentof the examination region. The second electric field intensity is lessthan the first electric field intensity. In an embodiment, the otherarbitrary transverse segment abuts the selected arbitrary examinationsegment.

In an embodiment of the system 905, the localized pulse of theradiofrequency magnetic field B₁ includes (i) a first radiofrequencyelectric field intensity in the selected arbitrary examination segment,(ii) a second radiofrequency electric field intensity in a secondarbitrary transverse segment of the examination region abutting theselected arbitrary transverse segment, and (iii) a third radiofrequencyelectric field intensity in a third arbitrary transverse segment of theexamination region abutting the selected arbitrary transverse segmentand positioned opposite to the second arbitrary transverse segment. Inthis embodiment, the second and third radiofrequency electric fieldintensities are each less than the first radiofrequency electric fieldintensity.

In an embodiment of the system 905, the localized pulse of theradiofrequency magnetic field B₁ is configured to produce a firstspecific absorption rate (SAR) in a potential examination subjectlocated in the selected arbitrary examination segment and to produce asecond SAR in another arbitrary transverse segment of the examinationregion. In this embodiment, the second SAR is less than the first SAR.SAR typically is expressed as watts per kilogram.

In an embodiment of the system 905, a possible amplification stateincludes an on-state or an off-state. In an embodiment, theamplification state includes an off-state for at least one of the threegroups 920. In an embodiment, the B₁ localization control signal definesan amplification state and an amplification parameter assigned to eachgroup of the at least two groups. In an embodiment, the B₁ localizationcontrol signal defines a respective power distribution and phase delays(including zero and non-zero phase delays) of a particular incidentpulse of radiofrequency electromagnetic waves to each group of the atleast two groups. In an embodiment, the amplification parameter includesan amplitude or a phase assigned to each group of the at least twogroups.

In an embodiment of the system 905, the control circuit 972 includes acontrol circuit configured to (i) select an arbitrary examinationsegment transverse to the z-axis 318 responsive to data indicative of atransverse slice selected for examination, (ii) select at least onegroup of the at least two groups 920 to deliver a localized pulse ofradiofrequency magnetic field B₁ to the selected arbitrary examinationsegment, (iii) define a pulse of radiofrequency magnetic field B₁localized to the selected arbitrary examination segment and having amagnetic field intensity sufficient to excite a detectable magneticresonance in magnetically active nuclei located within the selectedarbitrary segment, and in response thereto (iv) generate the B₁localization control signal defining an amplification state assigned toeach group of the at least two groups. In an embodiment, the (iii)define includes define an optimized pulse of radiofrequency magneticfield B₁ localized to the selected arbitrary examination segment.

In an embodiment of the system 905, the first group of the at least twogroups 920 includes a first group of at least two artificiallystructured unit electromagnetic cells 924 configured to generate amagnetic field-dominant radiofrequency near-field whose magnetic andelectric field intensities are such that (B₁c)/E₁>1, and a second groupof the at least two groups includes at least two artificially structuredunit electromagnetic cells configured to generate an electric fieldcounteracting a non-vanishing electric field generated by the firstgroup of artificially structured electromagnetic unit cells.

In an embodiment, the system 905 includes a receiver 974 configured toreceive data indicative of a location along the z-axis 318 of thetransverse slice selected for examination. In an embodiment, the controlcircuit 972 is configured to select the arbitrary examination segmentresponsive to the data indicative of the location of the slice along thez-axis.

In an embodiment of the system 905, the at least two artificiallystructured electromagnetic unit cells of each group include at least twoassemblages of artificially structured electromagnetic unit cells 1215as described in conjunction with FIG. 12. In this embodiment, eachassemblage of at least two artificially structured electromagnetic unitcells includes a first artificially structured electromagnetic unit cell1222 configured to generate the pulse of the radiofrequency magneticfield B₁ and a second artificially structured electromagnetic unit cell1224 configured to generate an electric field E counteracting anon-vanishing electric field component generated by the firstartificially structured electromagnetic unit cell.

In an embodiment of the system 905, the generated B₁ localizationcontrol signal defines an amplification state and a phase assigned toeach the at least two artificially structured electromagnetic unit cellsof each assemblage of the at least two assemblages of each group. Thedefined amplification states and phases collectively defining anoptimized pulse of the radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment and having a selected E/(Bc)ratio averaged over the selected arbitrary examination segment. In anembodiment, the selected E/(Bc) ratio includes a minimized E/(Bc) ratioaveraged over the selected arbitrary examination segment. In anembodiment, the selected E/(Bc) ratio includes an optimized E/(Bc) ratioaveraged over the selected arbitrary examination segment. In anembodiment, the optimized E/(Bc) ratio is selected responsive to a setof configurable rules. In an embodiment, the optimized E/(Bc) ratio isselected responsive to a matrix factorization, or a matrix decompositionbased optimization technique.

In an embodiment of the system 905, the at least two artificiallystructured electromagnetic unit cells 924 include at least twoelectrically-controllable, artificially structured electromagnetic unitcells. In an embodiment, the at least two artificially structuredelectromagnetic unit cells of a group include at least two randomlyaccessible, electrically-controllable, artificially structuredelectromagnetic unit cells. In an embodiment, the at least twoelectrically-controllable, artificially structured electromagnetic unitcells are configured to generate a gradient in the radiofrequencymagnetic field B₁ intensity across the selected transverse segment.

FIG. 10 illustrates an example operational flow 1000. After a startoperation, the operational flow includes reception operation 1010. Thereception operation includes receiving a pulse of radiofrequencyelectromagnetic waves from a radiofrequency signal generator or signalsynthesizer component of a magnetic resonant imaging or a nuclearmagnetic resonant device. In an embodiment, the reception operation maybe implemented using the primary radiofrequency electromagnetic waveconducting structure 980 to receive the pulse of radiofrequencyelectromagnetic waves 992 as described in conjunction with FIG. 9. Achoice operation 1020 includes selecting an arbitrary examinationsegment transverse to a z-axis of a bore of the magnetic resonantimaging or the nuclear magnetic resonant device in response to dataindicative of a location of a transverse slice selected for examination.In an embodiment, the choice operation may be implemented using thecontroller 973 described in conjunction with FIG. 9. A localizationoperation 1030 includes generating a B₁ localization control signaldefining an amplification state assigned to each group of at least twogroups of at least two artificially structured electromagnetic unitcells. Each group of the at least two groups of the array issequentially positioned in a respective plane transverse to the z-axis.The amplification states collectively defining a localized pulse ofradiofrequency magnetic field B₁ transverse to the quasistatic magneticfield B₀ that is parallel to the z-axis of the bore. The localized pulsehaving an intensity sufficient to excite a detectable magnetic resonancein magnetically active nuclei located within the selected arbitraryexamination segment. In an embodiment, the localization operation may beimplemented using the controller 972 described in conjunction with FIG.9. A regulation operation 1040 includes switching an electronicallycontrollable radiofrequency amplifier of a group of at least two groupsto a state responsive to the B₁ localization control signal andrespectively amplifying the received pulse of radiofrequencyelectromagnetic waves in response thereto. For example, the amplifiermay be placed in an on-state, an off-state, or to a selectedamplification level state. In an embodiment, the regulation operationmay be implemented by using the control signal 973 to switch on at leastone of the amplifiers 960.1-960.5 described in conjunction with FIG. 9.A dissemination operation 1050 includes delivering the amplifiedreceived pulse of radiofrequency electromagnetic waves as an incidentamplified pulse of radiofrequency electromagnetic waves to the at leasttwo artificially structured electromagnetic unit cells of the group. Inan embodiment, the dissemination operation may be implemented using atleast one of the secondary radiofrequency electromagnetic waveconducting structure 982.1-982.5 described in conjunction with FIG. 9. Aconversion operation 1060 includes transforming, using the at least twoartificially structured electromagnetic unit cells of the group of atleast two groups, the incident amplified pulse of radiofrequencyelectromagnetic waves into the localized pulse of radiofrequencymagnetic field B₁. The conversion operation may be implemented using theat least two artificially structured electromagnetic unit cells 924 ofthe group of at least two groups 920 described in conjunction with FIG.9. The operational flow includes an end operation. In an embodiment, theoperational flow includes receiving the data indicative of the locationof the transverse slice selected for examination.

FIG. 11 illustrates an example apparatus 1100. The apparatus includesmeans 1110 for receiving a pulse of radiofrequency electromagnetic wavesfrom a radiofrequency signal generator or signal synthesizer componentof a magnetic resonant imaging or a nuclear magnetic resonant device.The apparatus includes means 1120 for selecting an arbitrary examinationsegment transverse to the z-axis of the bore of the magnetic resonantimaging or the nuclear magnetic resonant device in response to dataindicative of a location of a transverse slice selected for examination.The apparatus includes means 1130 for generating a B₁ localizationcontrol signal defining an amplification state assigned to each group ofat least two groups of at least two artificially structuredelectromagnetic unit cells of an array. Each group of the at least twogroups of the array is sequentially positioned in a respective planetransverse to the z-axis. The amplification states collectively defininga localized pulse of radiofrequency magnetic field B₁ orientatedtransverse to the quasistatic magnetic field B₀ parallel to the z-axisof the bore and having an intensity sufficient to excite a detectablemagnetic resonance in magnetically active nuclei located within theselected arbitrary examination segment. The apparatus includes means1140 for switching an electronically controllable radiofrequencyamplifier of a group of at least two groups to a state responsive to theB₁ localization control signal and respectively amplifying the receivedpulse of radiofrequency electromagnetic waves in response thereto. Theapparatus includes means 1150 for delivering the amplified receivedpulse of radiofrequency electromagnetic waves as an incident amplifiedpulse of radiofrequency electromagnetic waves to the at least twoartificially structured electromagnetic unit cells of the group. Theapparatus includes means 1160 for transforming, using the at least twoartificially structured electromagnetic unit cells of the group of atleast two groups, the incident amplified pulse of radiofrequencyelectromagnetic waves into the localized pulse of radiofrequencymagnetic field B₁.

FIG. 12 illustrates an example an apparatus 1205. The apparatusincluding an assemblage 1215 of artificially structured electromagneticunit cells 1220. The artificially structured electromagnetic unit cellsinclude a first artificially structured electromagnetic unit cellconfigured to transform incident radiofrequency electromagnetic waves1292 into a radiofrequency magnetic field B₁ perpendicular to the planeof the assemblage. The plane of the assemblage is illustrated as in theX-axis and Z-axis of the X—Y-Z axises 1292. The first artificiallystructured electromagnetic unit cell is illustrated by an artificiallystructured electromagnetic unit cell 1222.1. Another first artificiallystructured electromagnetic unit cell is illustrated by an artificiallystructured electromagnetic unit cell 1222.2. The artificially structuredelectromagnetic unit cells include a second artificially structuredelectromagnetic unit cell configured to transform another incidentradiofrequency electromagnetic waves into an electric field Ecounteracting a non-vanishing electric field component generated by thefirst artificially structured electromagnetic unit cell. The secondartificially structured electromagnetic unit cell is illustrated by anartificially structured electromagnetic unit cell 1224.1. Another secondartificially structured electromagnetic unit cell is illustrated by anartificially structured electromagnetic unit cell 1224.2. In anembodiment, second artificially structured unit cell may be loaded witha lumped capacitor to lower its resonance frequency. In an embodiment,the incident radiofrequency electromagnetic waves 1292 include theanother incident radiofrequency electromagnetic waves. In an embodiment,the another incident radiofrequency electromagnetic waves are differentfrom the incident radiofrequency electromagnetic waves 1292.

In an embodiment, the assemblage 1215 includes a planar assemblage ofthe artificially structured electromagnetic unit cells 1220. In anembodiment, the assemblage includes an arcuate assemblage 1220 ofartificially structured electromagnetic unit cells. In an embodiment,the array includes at least two assemblages of artificially structuredelectromagnetic unit cells. In an embodiment, the first artificiallystructured electromagnetic unit cell and the second artificiallystructured electromagnetic unit cell are respectively configured toproduce a selected E/(Bc) ratio in the radiofrequency magnetic field Bperpendicular to the plane of the assemblage. In an embodiment, thefirst artificially structured electromagnetic unit cell and the secondartificially structured electromagnetic unit cell are respectivelyconfigured to produce a selected minimized E/(Bc) ratio in theradiofrequency magnetic field B perpendicular to the plane of theassemblage.

In an embodiment, the counteracting electric field E includes anoffsetting electric field E. In an embodiment, the counteractingelectric field E includes an electric field E at least partiallycancelling a non-vanishing electric field component generated by thefirst artificially structured electromagnetic unit cell. In anembodiment, the non-vanishing electric field includes a non-vanishingelectric field component generated by electric dipole or multipolemoments by the first artificially structured electromagnetic unit.

In an embodiment, the second artificially structured electromagneticunit cell (1224.1 or 1224.2) includes a one-dimensional ortwo-dimensional split ring resonator unit cell optimized for highelectric field intensity. For example, the SRR may include an “H” shapewith shoulder plates pointed centrally.

In an embodiment, each assemblage 1215 includes two first artificiallystructured electromagnetic unit cells 1222, and one second artificiallystructured electromagnetic unit cell 1224. In an embodiment, eachassemblage includes two first artificially structured electromagneticunit cells arranged in a first row, and two second artificiallystructured electromagnetic unit cells arranged in a second row. In anembodiment, each assemblage includes two first artificially structuredelectromagnetic unit cells arranged on a first diagonal, and two secondartificially structured electromagnetic unit cell arranged on a seconddiagonal orthogonal to the first diagonal.

In an embodiment, the first artificially structured electromagnetic unitcell 1222 is configured to transform incident radiofrequencyelectromagnetic waves into a radiofrequency magnetic field B₁ having afirst component perpendicular (Y-axis) to the plane of the planar arrayand a second component orthogonal (X-axis or Z-axis) to the plane (X-Z)of the planar array. In an embodiment, the first artificially structuredelectromagnetic unit cell is configured to transform incidentradiofrequency electromagnetic waves into a radiofrequency magneticfield B₁ having components in all three mutually orthogonal directions.In an embodiment, the first artificially structured electromagnetic unitcell includes a pair of artificially structured electromagnetic unitscells. A first cell of the pair is configured to transform incidentradiofrequency electromagnetic waves into a radiofrequency magneticfield B₁ perpendicular to the plane of the planar array, and a secondcell of the pair is configured to transform incident radiofrequencyelectromagnetic waves into a radiofrequency magnetic field B₁ orthogonalto the plane of the planar array. In an embodiment, the firstartificially structured electromagnetic unit cell includes threeartificially structured electromagnetic units cells configured totransform incident radiofrequency electromagnetic waves into aradiofrequency magnetic field B having components in all three mutuallyorthogonal directions.

In an embodiment, each assemblage 1215 of the artificially structuredelectromagnetic unit cells 1220 includes a first layer of artificiallystructured electromagnetic unit cells configured to transform incidentradiofrequency electromagnetic waves into a radiofrequency magneticfield B₁ perpendicular or normal to the plane of the planar array. Eachassemblage also includes a second layer of artificially structuredelectromagnetic unit cells configured to transform the incident pulse ofradiofrequency electromagnetic waves into an electric field Ecounteracting a non-vanishing electric field component generated by thefirst layer of artificially structured electromagnetic unit cells.

In an embodiment, the apparatus 1205 includes a radiofrequencyelectromagnetic wave conducting structure 1280 configured to distributethe radiofrequency electromagnetic waves 1292 as incident radiofrequencyelectromagnetic waves to the assemblage 1215 of at least two groups 1120of artificially structured electromagnetic unit cells 1220.

In an embodiment, the assemblage 1215 of artificially structuredelectromagnetic unit cells 1220 is capable of creating essentially anyquasistatic field configuration compatible with Maxwell's equations. Inan embodiment of the apparatus 1205, electric fields in the near-fieldmay be sculpted almost independently from the magnetic fields. This ispossible because of the weak coupling between magnetic and electricfields in the near-field. The ability to control or limit electric fieldintensity relatively independently of magnetic field intensity is usefulin a variety of biomedical applications. For example, this will allowrelatively strong magnetic fields to be directed at patients while anelectric field normally associated with the strong magnetic field issignificantly reduced, thus improving patient safety and comfort. Forexample, this will allow the use of higher-intensity magnetic fieldscapable of providing better quality images or faster image acquisitionrates, without increasing the patient's discomfort or exceeding themaximum permissible exposure to the electric fields or maximum safe SARlevels. For example, applications of the assemblage include non-invasivewireless charging of or communication with surgical microbots whose sizelimits or prohibits an on-board battery. For example, applications ofthe assemblage include magnetic induction tomography (MIT),magneto-acoustic tomography (MAT) (also known as magneto-inductiveultrasonography), or transcranial magnetic stimulation (TMS). Forexample, applications of the assemblage include using the same apparatusto perform several actions on a patient. For example, a single apparatusmay perform MRI-guided TMS, or MAT-guided micro-robot ornano-robot-assisted surgery.

FIG. 12 also illustrates an alternative embodiment of the exampleapparatus 1205. The apparatus includes an array 1210 of at least twoassemblages 1215 of the at least two artificially structuredelectromagnetic unit cells 1220. Each assemblage of the at least twoassemblage of artificially structured electromagnetic unit cellsincluding a first artificially structured electromagnetic unit cell 1222configured to transform incident radiofrequency electromagnetic wavesinto a radiofrequency magnetic field B₁ perpendicular to the plane ofthe assemblage. Each assemblage of the at least two assemblage ofartificially structured electromagnetic unit cells including a secondartificially structured electromagnetic unit cell 1224 configured totransform the incident radiofrequency electromagnetic waves into anelectric field E counteracting a non-vanishing electric field componentgenerated by the first artificially structured electromagnetic unitcell. For example the array 1210 may be at least similar to the array610 of at least two groups 620 described in conjunction with FIG. 6,wherein each group include a respective assemblage of the artificiallystructured electromagnetic unit cells 1220. For example the array 1210may be at least similar to the array 910 of at least two groups 920described in conjunction with FIG. 9, wherein each group include arespective assemblage of the artificially structured electromagneticunit cells 1220.

The apparatus 1205 includes a radiofrequency electromagnetic waveconducting structure 1280 configured to distribute the radiofrequencyelectromagnetic waves 1292 as incident radiofrequency electromagneticwaves to each assemblage of the at least two assemblages of artificiallystructured electromagnetic unit cells 1220. In an embodiment, the array1210 includes a planar or an arcuate array of the at least twoassemblages 1215 of artificially structured electromagnetic unit cells1220.

FIG. 13 illustrates an example operational flow 1300. After a startoperation, the operational flow includes dissemination operation 1310.The dissemination operation includes distributing radiofrequencyelectromagnetic waves as incident radiofrequency electromagnetic wavesto at least two assemblages of artificially structured electromagneticunit cells of an array. In an embodiment, the dissemination operationmay be implemented using the radiofrequency electromagnetic waveconducting structure 1280 as described in conjunction with FIG. 12. Afirst conversion operation 1320 includes transforming, using a firstartificially structured electromagnetic unit cell of each assemblage ofthe at least two assemblages, the incident radiofrequencyelectromagnetic waves into a radiofrequency magnetic field Bperpendicular to the plane of the planar array. In an embodiment, thefirst conversion operation may be implemented using the firstartificially structured electromagnetic unit cell described inconjunction with FIG. 12, such as the first unit cell 1222.1. A secondconversion operation 1330 includes transforming, using a secondartificially structured electromagnetic unit cell of each assemblage ofthe at least two assemblages, the incident radiofrequencyelectromagnetic waves into an electric field E counteracting anon-vanishing electric field component generated by the firstartificially structured electromagnetic unit cell. In an embodiment, thefirst conversion operation may be implemented using the secondartificially structured electromagnetic unit cell described inconjunction with FIG. 12, such as the first unit cell 1224.1. Theoperational flow includes an end operation.

FIGS. 2 and 12 illustrate an alternative embodiment of the exampleapparatus 310. The apparatus includes the array 1210 of at least twoassemblages 1215 of artificially structured electromagnetic unit cells1220. Each assemblage is configured to generate a pulse ofradiofrequency magnetic field B₁ 328 orientated transverse to the z-axis318 of the bore 316 of a magnetic resonant imaging or a nuclear magneticresonant device 300. Each assemblage of artificially structuredelectromagnetic unit cells including (i) a first artificially structuredelectromagnetic unit cell 1222 configured to transform an incident pulseof radiofrequency electromagnetic waves into the pulse of theradiofrequency magnetic field B₁ and (ii) a second artificiallystructured electromagnetic unit cell 1224 configured to transform theincident pulse of radiofrequency electromagnetic waves into an electricfield E counteracting a component of a non-vanishing electric fieldgenerated by the first artificially structured electromagnetic unitcell. The pulse of the radiofrequency magnetic field B₁ collectivelygenerated by the first artificially structured electromagnetic unit cellhaving a magnetic field intensity sufficient to excite a magneticresonance in magnetically active nuclei located within the bore.

The apparatus 310 includes the radiofrequency electromagnetic waveconducting structure 380 configured to distribute the pulse ofradiofrequency electromagnetic waves 392 as an incident pulse ofradiofrequency electromagnetic waves to each of the at least twoassemblages of artificially structured electromagnetic unit cells.

In an embodiment, the array 1215 is configured to generate a pulse ofradiofrequency magnetic field B₁ orientated transverse to thequasistatic magnetic field B₀ parallel to the z-axis of the bore of amagnetic resonant imaging or a nuclear magnetic resonant device.

FIG. 14 illustrates an example operational flow 1400. After a startoperation, the operational flow includes a reception operation 1410. Thereception operation includes receiving a pulse of radiofrequencyelectromagnetic waves from a radiofrequency signal generator orsynthesizer component of a magnetic resonant imaging or a nuclearmagnetic resonant device. In an embodiment, the reception operation maybe implemented using the radiofrequency electromagnetic wave conductingstructure 380 described in conjunction with FIG. 2. A disseminationoperation 1420 includes distributing the received pulse ofradiofrequency electromagnetic waves as an incident pulse ofradiofrequency electromagnetic waves to at least two assemblages ofartificially structured electromagnetic unit cells. In an embodiment,the dissemination operation may be implemented using the radiofrequencyelectromagnetic wave conducting structure 380 or 1280 to distribute thepulse 1292 to at least two assemblages of artificially structuredelectromagnetic unit cells 1220 of the array 1220 described inconjunction with FIG. 12. A first conversion operation 1430 includestransforming, using a first artificially structured electromagnetic unitcell of each assemblage of the at least two assemblages, the incidentpulse of radiofrequency electromagnetic waves into a pulse of aradiofrequency magnetic field B₁ orientated transverse the z-axis of tothe bore of the magnetic resonant imaging or the nuclear magneticresonant device. In an embodiment, the first conversion operation may beimplemented using the first artificially structured electromagnetic unitcell described in conjunction with FIG. 12, such as the first unit cell1222.1. A second conversion operation 1440 includes transforming, usinga second artificially structured electromagnetic unit cell of eachassemblage of the at least two assemblages, the incident radiofrequencyelectromagnetic waves into an electric field E counteracting anon-vanishing electric field component generated by the firstartificially structured electromagnetic unit cell. In an embodiment, thefirst conversion operation may be implemented using the secondartificially structured electromagnetic unit cell described inconjunction with FIG. 12, such as the first unit cell 1224.1. The pulseof radiofrequency magnetic field B₁ collectively generated by theartificially structured electromagnetic unit cells having a magneticfield intensity sufficient to excite a magnetic resonance inmagnetically active nuclei located within at least a portion of anexamination region located within the bore. The operational flowincludes an end operation.

In an embodiment, the first conversion operation 1430 includestransforming, using a first artificially structured electromagnetic unitcell of an assemblage of the at least two assemblages, the incidentpulse of radiofrequency electromagnetic waves into a pulse of aradiofrequency magnetic field B₁ orientated transverse to a segment ofthe quasistatic magnetic field B₀ parallel to the z-axis and spatiallyproximate to the group.

FIGS. 8 and 12 illustrate an alternative embodiment of the examplesystem 602 that includes an alternative embodiment of the exampleapparatus 605 configured to generate a radiofrequency magnetic field B₁in a magnetic resonant imaging or a nuclear magnetic resonant device,for example, such as the magnetic resonant imaging or a nuclear magneticresonant device described in conjunction with the environment 200 inFIG. 1. The system includes an array 1210 of at least two assemblages1215 of artificially structured electromagnetic unit cells 1220. Eachassemblage of the at least two assemblages is configured to besequentially positioned in a respective plane transverse to the z-axis318 of the bore 316 of a magnetic resonant imaging or a nuclear magneticresonant device. The artificially structured electromagnetic unit cellsinclude a first artificially structured electromagnetic unit cellconfigured to transform an incident pulse of radiofrequencyelectromagnetic waves 1292 into a radiofrequency magnetic field Bperpendicular to the plane of the assemblage. The first artificiallystructured electromagnetic unit cell is illustrated by an artificiallystructured electromagnetic unit cell 1222.1. Another first artificiallystructured electromagnetic unit cell is illustrated by an artificiallystructured electromagnetic unit cell 1222.2. The artificially structuredelectromagnetic unit cells include a second artificially structuredelectromagnetic unit cell configured to transform the incident pulseradiofrequency electromagnetic waves into an electric field Ecounteracting a non-vanishing electric field component generated by thefirst artificially structured electromagnetic unit cell. The secondartificially structured electromagnetic unit cell is illustrated by anartificially structured electromagnetic unit cell 1224.1. Another secondartificially structured electromagnetic unit cell is illustrated by anartificially structured electromagnetic unit cell 1224.2.

The system 602 includes the radiofrequency electromagnetic waveconducting structure 1280 configured to distribute the pulse ofradiofrequency electromagnetic waves 1292 as incident radiofrequencyelectromagnetic waves to a selectable assemblage of the at least twoassemblages in response to a B₁ localization control signal 673. Thesystem includes a control circuit 672 configured to generate the B₁localization control signal defining a respective power distribution ofa particular incident pulse of radiofrequency electromagnetic waves toeach assemblage of the at least two assemblages. The respective powerdistribution collectively defining a particular pulse of radiofrequencymagnetic field B₁ localized to a selected arbitrary examination segmenttransverse to the z-axis 318 and within an examination region of thebore 316. The localized magnetic field B₁ having an intensity sufficientto excite a detectable magnetic resonance in magnetically active nucleilocated within the selected arbitrary examination segment.

FIG. 15 illustrates an example operational flow 1500. After a startoperation, the operational flow includes a reception operation 1510. Thereception operation includes receiving a pulse of radiofrequencyelectromagnetic waves from a radiofrequency signal generator orsynthesizer component of a magnetic resonant imaging or a nuclearmagnetic resonant device. A dissemination operation 1520 includes thereceived pulse of radiofrequency electromagnetic waves as an incidentpulse of radiofrequency electromagnetic waves to a selected assemblageof at least two artificially structured electromagnetic unit cells of atleast two assemblages of artificially structured electromagnetic unitcells. A first conversion operation 1530 includes transforming, using afirst artificially structured electromagnetic unit cell of the selectedassemblage, the incident pulse of radiofrequency electromagnetic wavesinto a localized pulse of a radiofrequency magnetic field B₁ orientatedtransverse to a segment of the quasistatic magnetic field B₀ parallel tothe z-axis of a bore of the magnetic resonant imaging or the nuclearmagnetic resonant device, the localized pulse of the radiofrequencymagnetic field B₁ having a magnetic field intensity sufficient to excitea detectable magnetic resonance in magnetically active nuclei locatedwithin at least a portion of the transverse segment. The localized pulseof the radiofrequency magnetic field B₁ having a magnetic fieldintensity sufficient to excite a detectable magnetic resonance inmagnetically active nuclei located within at least a portion of thetransverse segment. A second conversion operation 1540 includestransforming, using a second artificially structured electromagneticunit cell of each assemblage of the at least two assemblages, theincident pulse of radiofrequency electromagnetic waves into an electricfield E counteracting a component of a non-vanishing electric fieldgenerated by the first artificially structured electromagnetic unit cellof each assemblage of the at least two assemblages. The operational flowincludes an end operation.

FIGS. 9 and 12 illustrate an alternative embodiment of the examplesystem 902 that includes an alternative embodiment of the exampleapparatus 905 configured to generate a radiofrequency magnetic field B₁in a magnetic resonant imaging or a nuclear magnetic resonant device,for example, such as the magnetic resonant imaging or a nuclear magneticresonant device described in conjunction with the environment 200 inFIG. 1. The system includes an array 1210 of the at least two groups920. Each group of the at least two groups includes at least twoassemblages 1215 of the artificially structured electromagnetic unitcells 1220. Each group of the at least two groups is configured to besequentially positioned in a respective plane transverse to the z-axis315 of the bore 316 of a magnetic resonant imaging or a nuclear magneticresonant device. Each group of at least two groups includes anelectronically controllable radiofrequency amplifier 960 configured toamplify the received pulse of radiofrequency electromagnetic waves 992in response to a B₁ localization control signal 973. Each group of atleast two groups includes a radiofrequency electromagnetic waveconducting structure 982 configured to deliver the amplified pulse ofradiofrequency electromagnetic waves as incident amplified pulse ofradiofrequency electromagnetic waves to the at least two assemblages ofartificially structured electromagnetic unit cells of the group. Eachassemblage of the artificially structured electromagnetic unit cellsincluding (i) a first artificially structured electromagnetic unit cell1222 configured to transform incident amplified pulse of radiofrequencyelectromagnetic waves into a pulse of radiofrequency magnetic field B₁transverse to a segment of the z-axis and spatially proximate to thegroup and (ii) a second artificially structured electromagnetic unitcell 1224 configured to transform incident amplified radiofrequencyelectromagnetic waves into an electric field counteracting anon-vanishing electric field component generated by the firstartificially structured electromagnetic unit cell.

The system 902 includes the control circuit 972 configured to select anarbitrary examination segment transverse to the quasistatic magneticfield B₀ parallel to the z-axis 318 in response to data indicative of atransverse slice selected for examination. The control circuit isconfigured to generate the B₁ localization control signal 973 definingan amplification state assigned to each amplifier 960. The amplificationstates collectively defining a pulse of radiofrequency magnetic field B₁localized to the selected arbitrary examination segment and having amagnetic field intensity sufficient to excite a detectable magneticresonance in magnetically active nuclei located within at least aportion of the transverse segment.

The foregoing detailed description has set forth various embodiments ofthe devices and/or processes via the use of block diagrams, flowcharts,and/or examples. Insofar as such block diagrams, flowcharts, and/orexamples contain one or more functions and/or operations, it will beunderstood by those within the art that each function and/or operationwithin such block diagrams, flowcharts, or examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or virtually any combination thereof.

All references cited herein are hereby incorporated by reference intheir entirety or to the extent their subject matter is not otherwiseinconsistent herewith.

In some embodiments, “configured” includes at least one of designed, setup, shaped, implemented, constructed, or adapted for at least one of aparticular purpose, application, or function.

It will be understood that, in general, terms used herein, andespecially in the appended claims, are generally intended as “open”terms. For example, the term “including” should be interpreted as“including but not limited to.” For example, the term “having” should beinterpreted as “having at least.” For example, the term “has” should beinterpreted as “having at least.” For example, the term “includes”should be interpreted as “includes but is not limited to,” etc. It willbe further understood that if a specific number of an introduced claimrecitation is intended, such an intent will be explicitly recited in theclaim, and in the absence of such recitation no such intent is present.For example, as an aid to understanding, the following appended claimsmay contain usage of introductory phrases such as “at least one” or “oneor more” to introduce claim recitations. However, the use of suchphrases should not be construed to imply that the introduction of aclaim recitation by the indefinite articles “a” or “an” limits anyparticular claim containing such introduced claim recitation toinventions containing only one such recitation, even when the same claimincludes the introductory phrases “one or more” or “at least one” andindefinite articles such as “a” or “an” (e.g., “a receiver” shouldtypically be interpreted to mean “at least one receiver”); the sameholds true for the use of definite articles used to introduce claimrecitations. In addition, even if a specific number of an introducedclaim recitation is explicitly recited, it will be recognized that suchrecitation should typically be interpreted to mean at least the recitednumber (e.g., the bare recitation of “at least two chambers,” or “aplurality of chambers,” without other modifiers, typically means atleast two chambers).

In those instances where a phrase such as “at least one of A, B, and C,”“at least one of A, B, or C,” or “an [item] selected from the groupconsisting of A, B, and C,” is used, in general such a construction isintended to be disjunctive (e.g., any of these phrases would include butnot be limited to systems that have A alone, B alone, C alone, A and Btogether, A and C together, B and C together, or A, B, and C together,and may further include more than one of A, B, or C, such as A₁, A₂, andC together, A, B₁, B₂, C₁, and C₂ together, or B₁ and B₂ together). Itwill be further understood that virtually any disjunctive word or phrasepresenting two or more alternative terms, whether in the description,claims, or drawings, should be understood to contemplate thepossibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.”

The herein described aspects depict different components containedwithin, or connected with, different other components. It is to beunderstood that such depicted architectures are merely examples, andthat in fact many other architectures can be implemented which achievethe same functionality. In a conceptual sense, any arrangement ofcomponents to achieve the same functionality is effectively “associated”such that the desired functionality is achieved. Hence, any twocomponents herein combined to achieve a particular functionality can beseen as “associated with” each other such that the desired functionalityis achieved, irrespective of architectures or intermedial components.Likewise, any two components so associated can also be viewed as being“operably connected,” or “operably coupled,” to each other to achievethe desired functionality. Any two components capable of being soassociated can also be viewed as being “operably couplable” to eachother to achieve the desired functionality. Specific examples ofoperably couplable include but are not limited to physically mateable orphysically interacting components or wirelessly interactable orwirelessly interacting components.

With respect to the appended claims the recited operations therein maygenerally be performed in any order. Also, although various operationalflows are presented in a sequence(s), it should be understood that thevarious operations may be performed in other orders than those which areillustrated, or may be performed concurrently. Examples of suchalternate orderings may include overlapping, interleaved, interrupted,reordered, incremental, preparatory, supplemental, simultaneous,reverse, or other variant orderings, unless context dictates otherwise.Use of “Start,” “End,” “Stop,” or the like blocks in the block diagramsis not intended to indicate a limitation on the beginning or end of anyoperations or functions in the diagram. Such flowcharts or diagrams maybe incorporated into other flowcharts or diagrams where additionalfunctions are performed before or after the functions shown in thediagrams of this application. Furthermore, terms like “responsive to,”“related to,” or other past-tense adjectives are generally not intendedto exclude such variants, unless context dictates otherwise.

While various aspects and embodiments have been disclosed herein, otheraspects and embodiments will be apparent to one skilled in the art. Thevarious aspects and embodiments disclosed herein are for purposes ofillustration and are not intended to be limiting, with the true scopeand spirit being indicated by the following claims.

What is claimed is:
 1. An apparatus comprising: a radiofrequencyelectromagnetic wave conducting structure configured to selectivelydistribute a received pulse of radiofrequency electromagnetic waves asan incident pulse of radiofrequency electromagnetic waves to a group ofat least two groups; the at least two groups of at least twoartificially structured electromagnetic unit cells, each group of the atleast two groups configured to be respectively linearly arranged withrespect to a z-axis of a bore of a magnetic resonant imaging or anuclear magnetic resonant device, each group of the at least two groupsof artificially structured electromagnetic unit cells configured totransform the incident pulse of radiofrequency electromagnetic wavesinto a pulse of radiofrequency magnetic field B₁ orientated transverseto a segment of the z-axis (hereafter “transverse segment”) andspatially proximate to the group.
 2. (canceled)
 3. (canceled) 4.(canceled)
 5. (canceled)
 6. (canceled)
 7. (canceled)
 8. (canceled) 9.(canceled)
 10. (canceled)
 11. (canceled)
 12. (canceled)
 13. (canceled)14. (canceled)
 15. (canceled)
 16. (canceled)
 17. (canceled) 18.(canceled)
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. A systemcomprising: a radiofrequency electromagnetic wave conducting structureconfigured to distribute a pulse of radiofrequency electromagnetic wavesas an incident pulse of radiofrequency electromagnetic waves to a groupof at least two selectable groups in response to a B₁ localizationcontrol signal; an array of the at least two selectable groups, eachgroup of the at least two selectable groups including at least twoartificially structured electromagnetic unit cells and configured to berespectively linearly arranged with respect to a z-axis of a bore of amagnetic resonant imaging or a nuclear magnetic resonant device, andeach group of the at least two artificially structured electromagneticunit cells respectively configured to transform the incident pulse ofradiofrequency electromagnetic waves into a pulse of radiofrequencymagnetic field B₁ orientated transverse to a segment of a z-axis(hereafter “transverse segment) and spatially proximate to the group;and a control circuit configured to generate the B₁ localization controlsignal defining a respective power distribution of a particular incidentpulse of radiofrequency electromagnetic waves to each group of the atleast two selectable groups, the respective power distributioncollectively defining a particular pulse of radiofrequency magneticfield B₁ localized to a selected arbitrary examination segmenttransverse to the z-axis and within an examination region of the bore,the localized magnetic field B₁ having an intensity sufficient to excitea detectable magnetic resonance in magnetically active nuclei locatedwithin the selected arbitrary examination segment.
 23. The system ofclaim 22, wherein each group of the at least two selectable groups isrespectively individually accessible or controllable independent oftheir respective location or sequence in the array.
 24. (canceled) 25.(canceled)
 26. (canceled)
 27. (canceled)
 28. The system of claim 22,wherein the selected arbitrary examination segment includes within itsz-axis boundaries a transverse slice of the examination region selectedfor examination.
 29. (canceled)
 30. The system of claim 22, furthercomprising: a receiver configured to receive data indicative of alocation along the z-axis of the transverse slice selected forexamination.
 31. (canceled)
 32. The system of claim 22, wherein thelocalized pulse of the radiofrequency magnetic field B₁ produces aquasi-focused radiofrequency magnetic field B₁ localized to include theselected arbitrary examination segment.
 33. (canceled)
 34. (canceled)35. (canceled)
 36. (canceled)
 37. (canceled)
 38. The system of claim 22,wherein the localized pulse of the radiofrequency magnetic field B₁includes a first radiofrequency electric field E₁ intensity in theselected arbitrary examination segment and includes a secondradiofrequency electric field E₂ intensity in a second arbitrarytransverse segment of the examination region, the second radiofrequencyelectric field intensity less than the first radiofrequency electricfield intensity.
 39. (canceled)
 40. (canceled)
 41. The system of claim38, wherein the second radiofrequency electric field intensity is lessthan 66% of the first radiofrequency electric field intensity. 42.(canceled)
 43. (canceled)
 44. The system of claim 22, wherein thelocalized pulse of the radiofrequency magnetic field B₁ includes (i) afirst radiofrequency electric field E₁ intensity in the selectedarbitrary examination segment, (ii) a second radiofrequency electricfield E₂ intensity in a second arbitrary transverse segment of theexamination region abutting the selected arbitrary transverse segment,and (iii) a third radiofrequency electric field E₃ intensity in a thirdarbitrary transverse segment of the examination region abutting theselected arbitrary transverse segment and positioned opposite to thesecond arbitrary transverse segment, the second and third radiofrequencyelectric field intensities each less than the first radiofrequencyelectric field intensity.
 45. (canceled)
 46. (canceled)
 47. (canceled)48. (canceled)
 49. The system of claim 22, wherein the localized pulseof the radiofrequency magnetic field B₁ is configured to produce a firstspecific absorption rate (SAR) in the selected arbitrary examinationsegment and to produce a second SAR in another arbitrary transversesegment of the examination region, the second SAR less than the firstSAR.
 50. The system of claim 49, wherein the second SAR is less than 66%of the first SAR.
 51. (canceled)
 52. (canceled)
 53. The system of claim22, wherein the respective power distribution further includes arespective power distribution collectively defining a particular pulseof radiofrequency magnetic field B₁ producing a minimized specificabsorption rate (SAR) in the selected arbitrary examination segment. 54.The system of claim 53, wherein the defined particular pulse ofradiofrequency magnetic field B₁ is configured in response to amodel-based estimation of the localized pulse respective powerdistribution providing the minimized SAR.
 55. (canceled)
 56. (canceled)57. (canceled)
 58. (canceled)
 59. The system of claim 53, wherein therespective power distribution is responsive to acontemporaneously-determined distribution of a radiofrequency magneticfield B₁ localized to the selected arbitrary examination segment withthe minimized SAR.
 60. The system of claim 59, wherein thecontemporaneously-determined distribution is responsive to datacontemporaneously received from at least one radiofrequency electricfield sensor.
 61. (canceled)
 62. (canceled)
 63. The system of claim 53,wherein the respective power distribution is selected responsive to anoptimization technique.
 64. (canceled)
 65. (canceled)
 66. (canceled) 67.(canceled)
 68. The system of claim 22, wherein the respective powerdistribution further includes a respective power distributioncollectively defining a particular pulse of radiofrequency magneticfield B₁ producing a selected ratio of a total specific absorption rate(SAR) produced in an examination subject divided by an average total SARproduced in the selected arbitrary examination segment of theexamination subject.
 69. (canceled)
 70. (canceled)
 71. (canceled) 72.(canceled)
 73. The system of claim 68, wherein the selected ratio isselected responsive to an optimization technique.
 74. (canceled)
 75. Thesystem of claim 22, wherein the radiofrequency magnetic field B₁includes a pulse of tunable radiofrequency magnetic field B₁. 76.(canceled)
 77. The system of claim 22, wherein the radiofrequencyelectromagnetic wave conducting structure is configured to receive thepulse of radiofrequency electromagnetic waves from a radiofrequencypower amplifier component associated with the magnetic resonant imagingor the nuclear magnetic resonant device.
 78. The system of claim 22,wherein the radiofrequency electromagnetic wave conducting structureincludes an electronically controllable switch responsive to the B₁localization control signal and coupled between a primary portion of theradiofrequency electromagnetic wave conducting structure and a secondaryportion of the radiofrequency electromagnetic wave conducting structure,the secondary portion coupled to a group of the at least two groups. 79.(canceled)
 80. (canceled)
 81. (canceled)
 82. (canceled)
 83. The systemof claim 22, wherein the respective power distribution defines aparticular pulse of radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment and having a substantiallyuniform magnetic field intensity.
 84. (canceled)
 85. (canceled)
 86. Thesystem of claim 83, wherein the substantially uniform magnetic fieldintensity includes less than an approximately five percent variation inthe radiofrequency magnetic field B₁ intensity across the selectedarbitrary examination segment.
 87. (canceled)
 88. The system of claim83, wherein the substantially uniform magnetic field intensity includesa variation in the radiofrequency magnetic field B₁ intensity across theselected arbitrary examination segment by a factor of less than ten. 89.The system of claim 22, wherein the respective power distributionincludes a model-based estimation of a respective power distributionproviding a pulse of radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment.
 90. The system of claim 89,wherein the model-based estimation is responsive to a set ofconfigurable rules.
 91. The system of claim 89, wherein the model-basedestimation of a respective power distribution is selected from a bestavailable distribution scheme from at least two available distributionschemes.
 92. (canceled)
 93. The system of claim 89, wherein themodel-based estimation of a respective power distribution is responsiveto a contemporaneously-determined distribution of a radiofrequencymagnetic field B₁ localized to the selected arbitrary examinationsegment.
 94. The system of claim 93, wherein the model-based estimationof a respective power distribution is responsive to datacontemporaneously received from at least one radiofrequency magneticfield sensor.
 95. The system of claim 93, wherein the model-basedestimation of a respective power distribution is responsive to adetected magnetic resonance in magnetically active nuclei located withinat least a portion of the examination region.
 96. The system of claim22, wherein the respective power distribution defines an optimized pulseof the radiofrequency magnetic field B₁ localized to the selectedarbitrary examination segment.
 97. (canceled)
 98. (canceled) 99.(canceled)
 100. (canceled)
 101. (canceled)
 102. (canceled) 103.(canceled)
 104. The system of claim 96, wherein the optimized pulseincludes a pulse of radiofrequency magnetic field B₁ localized to theselected arbitrary examination segment and having a magnetic fieldintensity sufficient to excite a detectable magnetic resonance inmagnetically active nuclei located within the selected arbitraryexamination segment, subject to a constraint limiting the electric fieldintensity within the transverse segment to less than a preselectedvalue.
 105. The system of claim 22, wherein the unit cells of each groupof the at least two groups include at least two electronicallycontrollable, artificially structured electromagnetic unit cells. 106.(canceled)
 107. The system of claim 105, wherein the respective powerdistribution defined by the control signal further includes a gradientcomponent of the radiofrequency magnetic field B₁ intensity orthogonalto the z-axis.
 108. The system of claim 107, wherein the gradientcomponent includes a gradient component in two respective directionsorthogonal to the z-axis.
 109. The system of claim 107, furthercomprising: a unit cell controller configured to electronically controlthe at least two electronically controllable, artificially structuredelectromagnetic unit cells of each group of the at least two selectablegroups in response to the gradient component of the control signal. 110.The system of claim 22, wherein the at least two artificially structuredelectromagnetic unit cells of each group of the at least two selectablegroups include a single layer of at least two artificially structuredelectromagnetic unit cells configured to generate a magnetic fieldcomponent orthogonal to the z-axis.
 111. The system of claim 22, whereinthe at least two artificially structured electromagnetic unit cells ofeach group of the at least two selectable groups include a first layerof at least two artificially structured electromagnetic unit cells and asecond layer of at least two artificially structured electromagneticunit cells, the unit cells of the first layer configured to generate amagnetic field component orthogonal to the z-axis, and the unit cells ofthe second layer configured to generate a magnetic field componentorthogonal to the magnetic field component of the first layer of unitcells.
 112. The system of claim 22, wherein the at least twoartificially structured electromagnetic unit cells of each group of theat least two selectable groups includes a first layer of at least twoartificially structured electromagnetic unit cells, a second layer of atleast two artificially structured electromagnetic unit cells, and athird layer of at least two artificially structured electromagnetic unitcells, the three layers of unit cells in combination configured togenerate magnetic field components in all three mutually orthogonalorientations.
 113. The system of claim 22, wherein the at least twoartificially structured electromagnetic unit cells of each group of theat least two selectable groups include a single layer of the at leasttwo artificially structured electromagnetic unit cells that incombination generate a radiofrequency magnetic field B₁ in twoorthogonal directions.
 114. The system of claim 22, wherein the at leasttwo artificially structured electromagnetic unit cells of each group ofthe at least two selectable groups include a single layer of the atleast two artificially structured electromagnetic unit cells that incombination generate a radiofrequency magnetic field B₁ in all threemutually orthogonal orientations.
 115. The system of claim 22, furthercomprising the magnetic resonant imaging or the nuclear magneticresonant device.
 116. A method comprising: receiving a pulse ofradiofrequency electromagnetic waves from a radiofrequency signalgenerator or signal synthesizer component of a magnetic resonant imagingor a nuclear magnetic resonant device; generating a B₁ localizationcontrol signal defining a respective power distribution of the pulse ofradiofrequency electromagnetic waves to each group of at least twoselectable groups of at least two artificially structuredelectromagnetic unit cells, each group of the at least two selectablegroups configured to be respectively linearly arranged with respect to az-axis of a bore of the magnetic resonant imaging or the nuclearmagnetic resonant device, the respective power distribution collectivelydefining a pulse of radiofrequency magnetic field B₁ localized to aselected arbitrary examination segment transverse to the z-axis andwithin an examination region of the bore, distributing the receivedpulse of radiofrequency electromagnetic waves as an incident pulse ofradiofrequency electromagnetic waves to a group of the at least twoselectable groups in accord with the B₁ localization control signal; andtransforming, using the at least two artificially structuredelectromagnetic unit cells of the group, the incident pulse ofradiofrequency electromagnetic waves into a localized pulse of aradiofrequency magnetic field B₁ orientated transverse to the selectedarbitrary examination segment and having an intensity sufficient toexcite a detectable magnetic resonance in magnetically active nucleilocated within the selected arbitrary examination segment.
 117. Themethod of claim 116, further comprising: selecting the arbitraryexamination segment responsive to data indicative of a location of aslice along the z-axis a transverse selected for examination.